Debate: MitraClip. The heart failure expert perspective

Acute myocardial infarction-related cardiogenic shock (AMI-CS) carries a dismal prognosis. Short-term mortality is in the range of 40% to 50%.1 Until recently, only percutaneous coronary intervention of the culprit lesion reduced mortality within randomized controlled trials (RCT).1 More recently, the active microaxial flow pump showed a mortality reduction at 6-month follow-up in the Danish German Shock trial (DanGer-Shock).2 However, this RCT was performed in a highly selected group of patients with ST-elevation myocardial infarction only and excluded patients with possible hypoxic brain injury.2 In addition, it remains unclear whether the positive results were influenced by: a) device design (loading vs unloading of the left ventricle), b) patient selection, and c) treatment bias.3 High expectations have also been placed on venoarterial extracorporeal membrane oxygenation (VA-ECMO), and its use has risen exponentially by up to 40 times in the last decade despite a lack of relevant evidence from RCTs.4

In contrast to microaxial flow pumps, the concept of VA-ECMO is to provide temporary complete circulatory and respiratory support during the critical first days as a bridge-to-recovery, bridge-to-decision, bridge-to-durable left ventricular assist device (LVAD), or bridge-to-transplantation.

QUESTION: What evidence exists for the use of ECMO in cardiogenic shock due to a myocardial infarction?

ANSWER: The evidence is relatively robust and is discussed in more detail below.

Another typical drawback of VA-ECMO is peripheral ischemic complications. Although a high rate (> 95%) of prophylactic antegrade perfusion cannulae was applied in ECLS-SHOCK, ischemic complications occurred with an OR of 2.86 (95%CI, 1.31-6.25), which was further aggravated in the IPD meta-analysis (OR 3.53; 95%CI, 1.70-7.34).8,9 VA-ECMO modifications to enable left ventricular (LV) unloading, such as VA-ECMO + Impella or VA-ECMO + intra-aortic balloon pump, should be further scrutinized, as despite potential benefits for LV recovery, they may increase bleeding risks even more.

Another problem with VA-ECMO was the prolongation of mechanical ventilation time and intensive care unit stay by roughly 2 days, which may also have caused more harm than benefit.8

Q.: In relation to the ECLS-SHOCK trial, what are the implications of its results on clinical practice and what do you consider the possible limitations of the study in this regard?

A.: When considering the implications of VA-ECMO on clinical practice, with evidence showing no mortality benefit but higher complications, guidelines usually classify this as a Class III A recommendation, advising against the routine use of VA-ECMO. However, the limitations or gaps in the evidence need to be discussed before final conclusions can be drawn.

On the limitations of the current evidence, negative or neutral trials often trigger discussions, particularly when the results do not concur with general perceptions, ie, VA-ECMO reduces CS mortality. A typical reflex is then to argue, using registry data, that RCTs are not valid.11

There are also other timing aspects to consider. In ECLS-SHOCK, VA-ECMO was started routinely after randomization. It remains unclear whether there is any clinical benefit to a watch and wait strategy and to decide for or against VA-ECMO only if there is further clinical and hemodynamic deterioration.

Q.: Is there any subgroup that may benefit from ECMO in this setting?

A.: In addition to the inclusion of resuscitated patients and timing aspects, the ECLS-SHOCK trial included patients with more advanced shock severity based on signs of tissue hypoperfusion. The SCAI shock classification was not in place at the start of the study and the definition is dynamic, which usually does not allow immediate staging.13 The distribution of the SCAI stages was therefore made retrospectively in ECLS-SHOCK using a modified post hoc definition.8 Some argue, therefore, that SCAI C patients were not sick enough to benefit from VA-ECMO or, in contrast, that SCAI stage E patients were in a futile situation. Irrespective of these considerations, no SCAI stage showed a benefit from VA-ECMO.

The question remains whether specific patient subgroups in AMI-CS benefit from VA-ECMO, as current guidelines do not mention patient selection.14 Importantly, there was no signal for a survival benefit of VA-ECMO in any of the subgroups analyzed.8,9

Q: Do you think there is a need for a new trial on the subject?

A.: THROUGH its mode of operation, VA-ECMO increases afterload. Multiple unloading strategies have been developed but these also increase invasiveness and possibly complications. In ECLS-SHOCK, unloading criteria were predefined, leading to a relatively low 6% rate of active unloading. However, more patients in the VA-ECMO group were treated with dobutamine, indicating medical unloading by increasing ventricular inotropy. When evaluating evidence for active unloading, it is also important to note that potential benefits were generated from retrospective observational studies only.15,16 A recent RCT comparing routine LV unloading by a transseptal left atrial cannula vs VA-ECMO alone showed no effect on mortality.17 This evidence suggests that further rigorous investigation is needed before the approach of using both VA-ECMO plus Impella for routine unloading can be adopted. Regarding the low use of durable LVADs or heart transplantation, in ECLS-SHOCK—similar to previous RCTs—the rate of patients receiving a durable LVAD or heart transplantation was < 2%. Advanced heart failure specialists often argue that VA-ECMO is mainly considered as a bridge-to-LVAD or transplantation and therefore that the trial was doomed to failure.11 Patients included in RCTs in AMI-CS are often older and not eligible for such treatment strategies. In addition, many of these patients have high rates of concomitant inflammation or infections precluding these advanced therapies.

In conclusion, for the vast majority of patients with AMI-CS, routine immediate VA-ECMO should be avoided. Future RCTs should define whether any subgroup can be identified and whether treatment modifications that reduce bleeding and limb ischemia complications or routine LV unloading strategies may alter the outcomes. In addition, currently evidence is only available for AMI-CS and not other causes of CS.

FUNDING

None.

STATEMENT ON THE USE OF ARTIFICIAL INTELLIGENCE

No artificial intelligence was used in the preparation of this article.

CONFLICTS OF INTEREST

None.

REFERENCES

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QUESTION: In your opinion, what conclusions can be drawn from the 2 ORBITA trials?1,2

ANSWER: The 2 ORBITA studies aim to settle the debate on the utility of coronary revascularization in patients with stable chronic angina and coronary artery lesions causing ischemia in that territory. The first ORBITA trial1—a double-blind, multicenter clinical trial published in 2018—randomized 230 patients with stable angina and at least 1 severe coronary stenosis (> 70%) to undergo percutaneous coronary intervention (PCI) or receive placebo to assess the symptom relief of angina. After being included in the study, both groups received a strategy of medical therapy optimization 6 weeks prior to randomization. There were no significant differences at the 6-month follow-up in the primary endpoint of exercise tolerance between the 2 groups. The authors concluded that the efficacy of invasive procedures should be determined with placebo control only (without pharmacological optimization). This is precisely what the recently published ORBITA-2 trial2 aimed to address. This trial randomized 301 patients in 14 centers in the United Kingdom to receive PCI or placebo. Two weeks before randomization, all antianginal drugs were discontinued. All patients were required to have significant coronary artery disease and evidence of ischemia in at least 1 vascular territory. Both groups received dual antiplatelet therapy (including the placebo group). The primary endpoint (assessment of angina, need for medication, and events after the 12-week follow-up) favored the PCI group vs the placebo group, with improvements in the follow-up ergometry and quality of life tests. The authors conclude that, in patients with stable angina, coronary artery disease, evidence of ischemia in that vascular territory, and not on antianginal drugs, PCI was more effective in reducing angina symptoms than placebo.

In my opinion, both studies confirm 2 issues: on the one hand, that the first-line therapy in patients with stable angina is optimal medical therapy; on the other hand, that PCI improves the symptoms, exercise capacity, and quality of life of patients who continue to experience angina or treatment-related adverse effects.

Q.: What would be the key features aspects of these 2 studies?

A.: Methodologically, the 2 studies have been conducted appropriately, but with very few patients. In the ORBITA trial1, recruitment was not easy (230 patients in 4 years, in 5 major centers in the United Kingdom), meaning there is a patient selection bias (generally less severe patients). Coronary artery disease was estimated visually (lesions > 70%), without the use of intracoronary imaging, and not all lesions were proximal, which likely have a higher ischemic burden. Finally, 85% of patients who did not undergo PCI, were eventually treated with percutaneous coronary revascularization during follow-up.

The ORBITA-2 trial2 addressed some of these limitations by using intravascular imaging and coronary physiology, which identify really significant lesions and avoid treating lesions that are functionally nonsevere, reducing events during follow-up.3-5 However, once again, and in 14 centers, enrolling 300 patients took more than 4 years. Ethical aspects of the study have been criticized, as comparison vs placebo and not vs optimal medical therapy left the placebo group without any treatment for angina and exposed them to unnecessary bleeding risks due to dual antiplatelet therapy. Nevertheless, conducting the study in this manner seems timely, since both the true utility of PCI and even the foundations of coronary physiology were questioned following the results of the ORBITA trial,1 suggesting that an increase in fractional flow reserve in an ischemic territory had no impact at all, which has been elucidated in the ORBITA-2 trial.2

Finally, perioperative myocardial infarction remains the weak point of coronary interventions in all clinical trials. The definition of “perioperative infarction” includes everything from Q-wave infarction related to loss of epicardial branch to mild troponin elevation (the threshold is 5 times higher than the upper limit, according to the current definition6) due to complications occurring during potentially treatable intervention with good final outcomes (branch dissection, no-reflow, compromised temporary flow, etc). Undoubtedly, this limits revascularization options (whether percutaneous or surgical) in all clinical trials. Therefore, it would be advisable to differentiate between the type of infarction, particularly those with the most prognostic implications.

Q.: What do you think these 2 studies contribute compared with the much larger ISCHEMIA trial?

A.: The ISCHEMIA trial,7 published in 2020, was much larger, with more than 5000 patients with stable coronary artery disease and moderate-to-severe ischemia, randomized to an initial invasive strategy with coronary angiography and revascularization, when necessary, along with medical therapy, or to an initially conservative strategy, with medical therapy alone and angiography if insufficient. The aim of the study was prognostic—not symptomatic—assessment, with a composite endpoint of cardiovascular death, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. After a median follow-up of 3.2 years, the initial invasive strategy did not reduce the risk of cardiovascular ischemic events or all-cause mortality compared with the conservative strategy.

Setting aside the limitations and potential criticisms of the ISCHEMIA trial,7 such as recruitment difficulties, very rigorous inclusion criteria, the absence of severe ischemia in a high percentage of cases, and that 25% of patients in the conservative treatment group eventually underwent revascularization, it is obvious that the aim of the study is very different from that of the ORBITA and ORBITA-2 trials.

In general, the prognosis of chronic coronary syndromes is good, but it is difficult to demonstrate prognostic differences in this subgroup of patients after a mean follow-up of just over 3 years. Furthermore, the ISCHEMIA trial included a group of patients who were heterogeneous in certain aspects features excluded those with more severe coronary artery disease (such as left main coronary artery disease) or ventricular dysfunction, in whom the prognostic impact of revascularization is known to be greater.

Another issue is symptom relief and quality of life. Indeed, the authors of the ISCHEMIA trial7 reported clinical implications and improvements in terms of quality of life. Although 35% of patients remained asymptomatic, the invasive strategy was associated with an improvement in angina-related quality of life, especially in patients with complete revascularization.8 This difference was greater for symptomatic patients.

The ORBITA trials focus on symptom relief in patients with chronic coronary syndromes, but with significantly fewer patients and shorter follow-up periods to demonstrate improvement in exercise capacity and quality of life, which were indeed observed in the secondary endpoints of the ISCHEMIA trial.

Q.: Based on all this evidence, what are the benefits, if any, of the invasive strategy over the conservative approach?

A.: The advantage of the invasive strategy over the conservative approach as first-line therapy has not been demonstrated in patients with chronic coronary syndromes. The cornerstone of therapy for patients with chronic angina is optimal medical therapy, as stated by clinical practice guidelines. In fact, the publication of the ORBITA trials has not changed these guidelines at all.

However, considering the results of these studies, we can be in no doubt that PCI is the best therapeutic option in patients who cannot control their symptoms with drugs, with drug-related adverse effects, or even those who simply do not want to continue taking drugs to control their symptoms. Revascularizing these patients is possible with good results and symptom relief.

We will have to wait for longer-term follow-up of the ISCHEMIA trial7 to evaluate whether coronary revascularization in patients with stable chronic angina has any prognostic impact. For the time being, until further evidence becomes available for confirmation, we know that the patients included in the study treated with complete revascularization experienced fewer events (cardiovascular death or myocardial infarction) during follow-up than those undergoing incomplete revascularization or an initial conservative strategy.9 Additionally, myocardial infarctions during follow-up (separating them from the perioperative infarctions with the above-mentioned implications) were also fewer in the group who initially underwent the invasive strategy.10

Finally, we should consider that all 3 studies included patients with generally low-risk chronic coronary syndromes, most with clearly demonstrated moderate ischemia, and single-vessel involvement, so their results are not generalizable to patients with more complex coronary artery disease, such as multivessel disease, left main coronary artery disease, or associated ventricular dysfunction.11 Therefore, the correct identification and characterization of coronary artery disease are important, which almost always requires noninvasive coronary angiography, or invasive angiography if the former is inconclusive. Another question arises: once coronary artery disease has been accurately assessed, should the patient undergo revascularization or should a conservative approach to their lesions be pursued for symptom relief? Or, depending on the extent or severity of the coronary artery disease and the myocardial territory at risk, is a more aggressive approach necessary, with either percutaneous or surgical revascularization?

Q.: What indications do you take into consideration in your routine clinical practice to decide which invasive approach to use in a patient with stable angina?

A.: The results obtained in the ORBITA trials maintain medical therapy as the first option for patients with chronic angina and relegate the invasive approach to those with symptoms that cannot be resolved despite optimal medical therapy. This would, therefore, be the indication in stable chronic angina. However, such results cannot be extrapolated to patients with multivessel disease and severe ischemia, so it would be a mistake to take them as a reference to stop performing coronary angiograms, which would imply avoiding the revascularization of patients at higher risk than indicated by their symptoms. Therefore, as always in medicine, each patient should be individually evaluated to determine who requires an earlier invasive approach based on their symptoms and multiple other factors. We’ll still have to wait for longer-term results, even for these lower-risk patients due to their lower ischemic burden, to see how the story ends.

FUNDING

None declared.

STATEMENT ON THE USE OF ARTIFICIAL INTELLIGENCE

No artificial intelligence was used in the preparation of this article.

CONFLICTS OF INTEREST

None declared.

REFERENCES

QUESTION: In your opinion, what conclusions can be drawn from the 2 ORBITA trials?1,2

ANSWER: The ORBITA trials focus on a specific aspect of the management of patients with acute coronary syndrome: the benefit in terms of symptom relief of angina.1,2 The first ORBITA trial1 is a double-blind, randomized, multicenter clinical trial, with 230 patients with severe single-vessel disease and ischemic symptoms that analyzed whether percutaneous coronary intervention (PCI) was associated with an improvement in angina-free exercise time compared with a placebo procedure.1 There were no statistically significant differences in the primary endpoint (differences in exercise increment on the stress test) at the 6-week follow-up between the 2 groups. The second ORBITA trial2, a double-blind, multicenter clinical trial, randomized 301 patients with exertional angina to undergo PCI or a placebo procedure.2 The methodology differs from that of ORBITA trial: all patients discontinued antianginal medication 2 weeks before randomization and were only included if they experienced angina throughout this period (assessed by a complex scoring system through a mobile application).3 Only patients with at least 1 severe coronary stenosis confirmed through physiological assessment were included; additionally, the 2 groups underwent the intervention (which was simulated in the group treated with the placebo procedure), and all patients received dual antiplatelet therapy. In total, 80% of patients had single-vessel disease, mostly involving the left anterior descending coronary artery, and complete revascularization was achieved in approximately 100% (using intracoronary imaging in 70% of PCIs). At the 12-week follow-up, patients treated with PCI experienced statistically significant greater angina relief, as well as improved exercise tolerance and quality of life than those in the placebo group.

Q.: What would be the key features of these 2 studies?

A.: Despite introducing the novel concept of simulating a PCI in the placebo group (thus avoiding the effect of attributing clinical improvement to the procedure per se), the main limitations of the first ORBITA trial were its small sample size and limited follow-up time. Moreover, the use of exercise tolerance with the stress test as the main study endpoint has been criticized due to its heterogeneity. Of note, 29% of patients had a negative functional flow reserve study (> 0.80), suggesting that there was no symptom improvement after PCI. Indeed, a prespecified substudy determined that, unlike angina (assessed by scores or exercise time), functional flow reserve did predict an improvement in ischemia (assessed by dobutamine stress echocardiography).4 All in all, the possible impact of this study on clinical practice seems limited.

Unlike the first trial, the main criticism of ORBITA-2—which evaluated patients with lesions in more than 1 vessel—is the discontinuation of antianginal treatment (ie, it compared PCI with patients without pharmacological treatment, unlike ORBITA, in which patients remained on optimal medical therapy), against the recommendation of clinical practice guidelines.5 Although the effect of PCI is expected to be immediate and sustained, the 12-week follow-up remains limited. Indeed, the main criticism that can be made of the study is its methodology: using a placebo procedure—not optimal medical therapy—for comparison may limit its clinical applicability. Nonetheless, the double-blind design of the study helps provide further evidence on PCI treatment in patients with coronary ischemia (both anatomical and functional) by improving the pathophysiology of the imbalance between oxygen supply and demand.

Q.: What do you think these 2 studies contribute compared with the much larger ISCHEMIA trial?

A.: In the context of chronic coronary syndrome, revascularization aims to provide 2 benefits: prognostic or symptomatic. In summary, the prognostic benefit of revascularization is well established in patients with severe left main or multivessel disease and left ventricular ejection fraction < 35%.5,6 However, there is more uncertainty surrounding the prognostic benefit in patients with extensive ischemic territory (a topic of discussion in the ISCHEMIA trial) and in evaluating the symptomatic benefit of the intervention regarding angina. The ISCHEMIA trial, with a larger sample size than the ORBITA trials, randomized a total of 5179 patients with stable coronary artery disease and moderate-to-severe ischemia on stress testing to an initial invasive or conservative strategy.7 After a median follow-up of 3.2 years, there were no significant differences between the 2 strategies in the primary endpoint (cardiovascular death, myocardial infarction, unstable angina hospitalization, heart failure, or resuscitated cardiac arrest). Although the multiple limitations of the study may affect the interpretation of its results (a high crossover rate between the 2 groups, up to 14% of the patients included in the study had mild or no ischemia, and the inclusion of perioperative infarctions which could bias the primary endpoint—more numerous in the invasive treatment group), patients randomized to the invasive treatment group showed greater symptomatic relief than those in the conservative treatment group. This benefit was greater in patients with more frequent episodes of angina at baseline and was less significant in asymptomatic patients, even with inducible ischemia.8

In my opinion, the main difference between the ORBITA and ISCHEMIA trials, beyond the sample size and limitations of the methodology of the former, is the blinding of patients undergoing invasive treatment in the ORBITA trials. Of note, symptoms are subjective and evaluating any intervention on cardiovascular events can have both a physiological component and a placebo effect. Therefore, we should welcome invasive studies to simulate the procedure in the control group because they allow testing the direct effect of the intervention on subjective endpoints, such as angina relief.

Q.: Based on all this evidence, what are the benefits, if any, of the invasive approach over the conservative approach?

A.: Current clinical practice guidelines (while awaiting the 2024 update from the European Society of Cardiology on the management of chronic coronary syndrome) state that the PCI should be reserved for patients who, despite being on optimal medical therapy, exhibit refractory symptoms,5,6 and the aforementioned evidence does not indicate the need to change this indication. The ORBITA trials have demonstrated that the relationship between epicardial coronary stenosis, ischemia, and symptoms is more complex than we had initially thought, while the ISCHEMIA trial has revealed the questionable impact of relieving ischemia on the incidence of events. Indeed, the severity of ischemia is a reflection of the burden of atherosclerotic disease, which is why only revascularizing the identified blockages will not have any clinical impact, as the intervention cannot change the underlying process.9 Moreover, an important point that should be made is that up to one-third of patients still experience angina symptoms despite successful revascularization.10 In this scenario, even the cost-effectiveness of the invasive approach vs optimal medical therapy remains to be elucidated.11 Therefore, beyond revascularization per se, an invasive hemodynamic study can provide valuable information to confirm the mechanism of ischemia (microcirculation abnormalities, vasomotor dysfunction, etc) and help optimize pharmacological treatment.

Q.: What indications do you take into consideration in your routine clinical practice to decide which invasive approach you should use in patients with stable angina?

A.: Setting aside scenarios where revascularization has previously shown prognostic improvement, as mentioned earlier, it seems reasonable to believe that the gold standard for stable angina should be pharmacological therapy. However, the fact that stable angina is a chronic disease, and the patient requires long-term antianginal drugs can complicate proper symptom control. Additionally, factors such as poor medication tolerability, suboptimal adherence, or the patient’s own preference must be considered. In all these situations, the invasive approach may be the preferred option.

FUNDING

None declared.

STATEMENT ON THE USE OF ARTIFICIAL INTELLIGENCE

Not used.

CONFLICTS OF INTEREST

None declared.

REFERENCES

QUESTION: Although we will discuss the aspects of 2 plaque modification techniques, please explain when you resort to intravascular imaging modalities in cases of calcified lesions and how that helps you.

ANSWER: Intracoronary imaging modalities (optical coherence tomography [OCT] and intravascular ultrasound [IVUS]) allow us to optimize percutaneous coronary interventions, and their use in complex lesions improves the patient’s prognosis.1 They facilitate the following aspects:2

• – Calcification detection and assessment: they have higher sensitivity and specificity than angiography for detecting calcium.3 Also, they allow the evaluation of calcification characteristics, and various scores4,5 have been developed that integrate variables associated with stent underexpansion.
• – Selection of plaque modification technique: intracoronary imaging findings have an impact on the strategy used, which is why the use of advanced imaging modalities is advised in the presence of risk criteria for stent underexpansion.2
• – Optimization of stent deployment: this is especially relevant in calcified lesions, which are the lesions most frequently associated with stent underexpansion, the parameter most often associated with stent failure.2 Other parameters that should also be assessed are proper stent apposition, lesion coverage, the absence of dissection, and significant hematoma around the edges.6

Q.: In your opinion, what are the advantages and disadvantages of ablation, whether rotational or orbital?

A.: Ablation therapies, such as rotational atherectomy (RA), or orbital atherectomy (OA), and Excimer laser coronary angioplasty (ELCA), offer several advantages over intracoronary lithotripsy (ICL):

• – Greater crossing ability: calcified lesions that result in very severe stenosis can be uncrossable with a balloon. In these lesions, the use of ablation techniques improves the rate of procedural success,7,8 and probably, costs and safety.
• – Ability to reduce plaque volume: an aspect that can be essential to optimize results.
• – Treatment of long lesions and multivessel disease: ICL balloons are short in length, and display a maximum of 120 pulses per balloon. Also, balloons should be sized in a 1:1 ratio with respect to the vessel diameter, which complicates their use in multiple lesions. With RA, and especially with OA and ELCA, we can safely and effectively treat segments of different calibers without increasing costs.
• The potential disadvantages of ablation therapies are:
• – A longer learning curve: despite having specific technical aspects, ICL does not significantly differ from the plain old balloon angioplasty. Consequently, since it became available, the use of ICL has grown exponentially.9 Ablation techniques require more operator (and nursing) training, which can limit their use.
• – Need for specific angioplasty guidewires: ELCA can be used with 0.014-inch angioplasty guidewires, but both RA and OA require specific guidewires, whose characteristics have been improved to allow their use throughout the entire procedure, as with conventional guidewires. However, they can lead to more difficulties in directly crossing lesions and make the procedure more cumbersome due to their greater length and lower support.
• – Side branch protection: although it can be performed using specific techniques, placing a side branch protection guidewire at a bifurcation during RA or OA is ill-advised. However, this is possible with ICL and ELCA.
• – Distal embolization: debris following the use of ablation techniques can be associated with slow-no reflow.

Q.: In which cases do you use ablation as a first-line approach? Are there any distinctions between rotational and orbital atherectomies?

A.: We usually use these techniques as the first-line approach in lesions so severely stenosed that they complicate balloon crossing or simply make it impossible (uncrossable lesions). The information provided by intracoronary imaging also plays a role in the decision to use ablation techniques as the first option. For some operators, the mere fact of being unable to cross the lesion with an IVUS or OCT probe is, per se, a criterion for using these ablation techniques. If intracoronary images are available, the presence of severity criteria, or the desire to reduce plaque volume encourages the use of advanced plaque modification therapies. Superficial concentric calcification with a very reduced luminal area would favor their use.

In terms of the differences among ablation techniques, in my opinion, the crossing ability of RA and ELCA is superior to that of OA, which therefore makes RA the preferred option to treat critical or uncrossable lesions. On the other hand, OA provides additional advantages over RA.2,10 In the first place, we can treat vessels from 2.5 mm to 4 mm due to its mechanism of action (rotation associated with elliptical orbits) with a single 1.25 mm crown (compatible with 6-Fr) without increasing the size of the guide catheter. Also, the elliptical motion of this crown not only allows for superficial calcium shaving (like RA), but also exerts pulsatile forces against the wall that can modify deeper calcium deposits.10,11 This orbital movement reduces wire bias compared with AR. Wire bias limits ablation, which is contact-dependent, to the vessel sector where the guide is located. In eccentric or nodular plaques, the guidewire may be displaced toward the opposite side of the vessel, thus minimizing the effect of RA on the plaque. Another interesting feature of OA is that the crown has a diamond coating across its entire surface (not just on the distal end, like RA crowns), allowing atherectomy to make forward and backward motions. The pullback mode modifies the ablation vector, potentially reducing wire bias even further. Furthermore, the debris produced by OA is theoretically smaller than those produced by RA. This, along with the fact that the crown does not impede coronary flow during atherectomy, reduces the risk of slow-no reflow and endothelial thermal injury.10

The main difference among ELCA, RA, and OA is that the former is the only ablation technique that is compatible with conventional coronary guidewires. Also, ELCA is compatible with 6-Fr guide catheters and allows for side branch protection. Also, it has beneficial effects in reducing thrombus and has proven to be safe and effective in peristent calcified lesions (restenosis or underexpansion).

Q.: Which calcified lesions benefit more from ablation compared with intracoronary lithotripsy?

A.: The calcified lesions that benefit the most from initial ablation rather than ICL are the most severely stenotic lesions, which are rarely crossable with a lithotripsy balloon as a first-line approach, and those with a large volume of plaque that we intend to reduce. Ablation techniques facilitate crossing these stenoses and are sufficient in many cases (when calcification is superficial, without significant thickness, and when calcified nodules are not involved) to allow adequate balloon or stent expansion, and complete the angioplasty. In addition, diffuse lesions in multiple segments, or vessels of different calibers can benefit more from ablation because they can be treated with a single RA, AO, or ELCA catheter.

Finally, although ICL can be safely performed in left main lesions, some patients (especially those with ventricular dysfunction or right coronary artery disease) can tolerate prolonged ICL balloon inflations poorly, and benefit from ablation techniques as a first option.

Q.: How do you integrate both ablation techniques into your protocol to treat calcified lesions?

A.: There are several algorithms for plaque modification techniques based on expert opinion. Evidence from comparative trials among the various techniques is scarce. Although randomized clinical trials are under way,12 the lesion characteristics, clinical context, available resources, and operator capabilities should always be taken into consideration.

Intracoronary imaging modalities are essential to select the strategy. In general, it is useful to apply the rule of 5N:2 advanced plaque modification techniques are advised to treat lesions where calcium occupies > 50% of the calcium arc (180°), extends longitudinally > 5 mm, is > 0.5 mm thick, or has calcified nodules. Additionally, the depth of calcium is important since some techniques, such as RA, can only modify superficial calcium.

Lesions that cause stenosis so severe that they cannot be crossed by IVUS or OCT probes will likely require RA, OA, or ELCA. RA may be the preferred choice for very stenotic lesions with superficial circumferential calcification, especially if they are uncrossable with a balloon and involve a nontortuous coronary segment. OA may be preferred to treat ostial, nodular lesions, or angulated segments. OA can also be useful in long lesions with significantly different proximal and distal vessel calibers. ELCA would be the preferred choice in lesions that cannot be crossed even with a microcatheter that allows exchange with RA or OA-specific guidewires. Also, ELCA could be the first option to treat peristent calcified lesions and those that combine calcium and thrombus.

ICL has the advantage of being a simpler technique and being able to modify deep calcium. ICL allows side branch protection without causing distal embolization of material. ICL can be the first choice if the lesion is crossable with a balloon, calcification is deep or thick, or it affects a true bifurcation. Additionally, ICL is an optimal technique for use in combination with ablation techniques when these do not allow adequate balloon expansion, or in complex lesions such as calcium nodules. Volume reduction and superficial calcium shaving with ablation techniques allows balloon ICL crossing. This completes plaque modification by fracturing deeper calcium deposits. This technique, initially described as rotatripsy13 (RA and ICL), is increasingly being used. Combinations of ELCA and ICL,14 or OA and ICL15 are less common, but have also been reported.

FUNDING

None declared.

STATEMENT ON THE USE OF ARTIFICIAL INTELLIGENCE

Artificial intelligence was not used in the preparation of this article.

CONFLICTS OF INTEREST

A. Jurado-Román is a proctor for Boston Scientific, Cardiovascular Systems, Inc., World Medica, and Philips-Biomenco.

REFERENCES