Insights from the AHA Scientific Statement on Managing Arrhythmias in Patients with Left Ventricular Assist Devices: Unique Challenges and Unanswered Questions

Left ventricular assist devices (LVADs) have become a mainstay therapy for patients with advanced heart failure by significantly reducing morbidity and mortality.^1-3 Consequently, the use of LVADs has increased rapidly over recent years.⁴ Given the high prevalence of both atrial and ventricular arrhythmias among LVAD recipients, clinicians are increasingly faced with the unique challenges of managing arrhythmias in this complex patient population. It is essential to realize that the usual arrhythmia management strategies that are used in advanced heart failure patients may not be applicable for recipients of LVADs. As such, the AHA Scientific Statement on "Device Therapy and Arrhythmia Management in Left Ventricular Assist Device Recipients"⁵ provides a timely overview of the existing literature and expert opinion on the unique aspects of treating patients with LVADs and arrhythmias. Given the general paucity of prospective clinical trial data on several key aspects of arrhythmia care for patients with LVADs, this document also highlights existing gaps in knowledge and outlines important areas for future study.

Are ICDs necessary in LVAD recipients?

An area of significant controversy is that of the role of implantable cardioverter-defibrillator (ICD) therapy in patients with LVADs. Most patients who receive LVADs will either already have an ICD present prior to LVAD implantation or are candidates for ICD implantation for primary prevention purposes on the basis of the presence of heart failure and severe systolic left ventricular dysfunction. However, the impact of ICD therapy on survival among LVAD recipients, particularly ICDs implanted for primary prevention purposes, is unclear. Patients who have LVADs can often tolerate sustained ventricular tachycardia (VT), and even ventricular fibrillation (VF) from a hemodynamic standpoint. The AHA statement summarizes the conflicting evidence on this issue. Although early single center observational studies showed a survival advantage among LVAD recipients with ICDs when compared to those without⁶, subsequent studies examining current generation continuous flow LVADs did not find that ICD therapy conferred survival benefit.^7,8 In fact, a study of 2209 patients from INTERMACS registry found that the presence of an ICD among continuous flow LVAD recipients was associated with increased mortality and unexpected death.⁹ However, interpretation of all of these data are limited by its retrospective design, which renders differentiation of causality from simple association impossible. Therefore, the AHA Scientific Statement recommends that the decision to implant an ICD in a LVAD recipient be based on an individualized, shared decision-making approach. In particular, ICDs should be more strongly considered in patients with LVADs and a history of poorly tolerated ventricular arrhythmias (VAs) due to syncope, hypotension or impaired LVAD flow. The role for primary prophylaxis ICD therapy for lower risk LVAD patients remains unclear.

Does cardiac resynchronization therapy have a role for patients with LVADs?

Although most patients with existing cardiac resynchronization therapy (CRT) devices continue CRT after LVAD implantation, the evidence for benefit of continued CRT in the setting of mechanical LV support is unclear. The AHA Scientific Statement summarizes the limited data that are available on comparisons of outcomes of patients with LVADs on continued CRT versus with CRT off. Other than a possible trend towards decreased ICD shocks in patients with continued CRT¹⁰, several studies have found no difference with respect to all-cause mortality and heart failure hospitalization between patients with continued CRT versus ICD only treatment.¹¹ However, these findings need to be interpreted with caution given the absence of large scale randomized data.

Are there special considerations to be made for patients with LVADs and ICDs?

For patients in whom ICDs have already been implanted, there are several important management considerations to be made after an LVAD is placed. As stated earlier, because ventricular arrhythmias are generally better tolerated in many LVAD patients, every effort should be made to minimize the likelihood of unnecessary ICD therapies. Going beyond existing recommendations for ICD programming strategies for standard patients, the AHA Scientific Statement advocates use of an “ultra-conservative” programming strategy for LVAD recipients by not only using high VF cut-off zone of 240 – 250 bpm, but also maximizing the detection time to longest programmable duration available on the ICD. Furthermore, multiple runs of anti-tachycardia pacing therapies should be programmed for the treatment of VT with the option of eliminating ICD shock treatment for these slower arrhythmias. However, caveats to this strategy remain when considering patients who have significant right ventricular dysfunction, pulmonary hypertension or poorly tolerated slow ventricular tachycardia.

In addition to ICD programming considerations, the issue of maximizing battery longevity is an especially critical one for patients with LVADs. Although it is clear that ICD generator replacements are associated with a significant risk of infection in the general ICD population, these procedures are theoretically associated with an even higher risk in the LVAD patient population due to the need for continued oral anticoagulation as well as LVAD-associated acquired Von Willebrand disorder. Therefore, the AHA Scientific Statement discusses the need for careful consideration of programming methods to increase battery longevity, which may even include deactivation of the LV lead given the absence of definitive data to suggest benefit of CRT in LVAD patients as discussed above. Furthermore, in patients with LVADs and no documented VAs who have primary prevention ICDs that have reached elective replacement indicator, it is not clear that ICD generator replacement is mandatory. All of these considerations underscore how standard paradigms of ICD management in patients with advanced heart failure can be challenged once an LVAD has been implanted.

How does LVAD implantation affect management of ventricular arrhythmias?

Although the circulatory support provided by an LVAD can render sustained ventricular tachycardia better tolerated by many LVAD patients, prolonged arrhythmia can still lead to symptoms, right ventricular failure, eventual hemodynamic compromise as well as ICD shocks. While the usual beta blockers and antiarrhythmic drugs can be used to treat VT in LVAD recipients, the high prevalence of severely diseased myocardium in the LVAD population can often lead to the presence of drug-refractory arrhythmias. The etiology of ventricular arrhythmias in LVAD patients are myriad and include: reentry due to abnormal baseline myocardial substrate, mechanical trauma related to the inflow cannula, bundle branch re-entry, and electrolyte abnormalities in the post-operative period.¹² It should be noted that the majority of LVAD patients who undergo VT ablation have VT arising from underlying myocardial substrate. This is an important consideration as patients who have significant substrate-based VT prior to LVAD implantation are likely to continue to have these arrhythmias even after implementation of circulatory support.

The AHA Scientific Statement reviews the limited data available on outcomes after catheter ablation of drug-refractory VAs in the LVAD population. Overall, acute procedural success rates have been reported to be between 77% and 86% with reasonable 1-year survival and acceptable complication rates. The AHA statement further highlights several challenges that are unique to the LVAD population when catheter ablation of VT is being considered. First, epicardial access can be impossible after LVAD implantation due to the presence of adhesions. Especially in patients with non-ischemic cardiomyopathy who have significant epicardial substrate for VT, endocardial catheter ablation can be ineffective. Therefore, surgical VT ablation can be considered as an option at the time of LVAD implantation, particularly in patients with high ventricular arrhythmia burden prior to surgery. Although outcomes data on this approach are lacking, recent data on the prognostic utility of epicardial scar characterization at time of LVAD implantation may point to a future role for empiric surgical ablation.¹³ It would be important to assess whether a more proactive approach with catheter ablation may yield better outcomes in the complex LVAD patient population. Second, artifact from the newer HeartMate 3 continuous flow LVAD can lead to significant high frequency noise that can affect surface electrocardiogram morphology assessment that can impact the ablation procedure. Altering the low pass filter can alleviate some of this artifact but can occur at the expense of losing some signal quality. Finally, technical procedural aspects of the procedure such as mode of access to the left ventricle (i.e. transseptal versus retrograde transaortic), catheter positioning close to the apical inflow cannula and attention to LVAD pump speed settings during the ablation are all important points to be considered.

Conclusions

In summary, the authors of this AHA Scientific Statement are to be commended for providing a, important summary of the existing evidence and expert opinion on arrhythmia management in LVAD patients. It should be emphasized that the breadth of evidence base in this burgeoning field remains limited and there are significant gaps in knowledge. Much of the data on ICD and CRT therapy as well as catheter ablation of arrhythmias in LVAD patients are based on observation studies. As such, a multidisciplinary, patient-centered approach with an emphasis on shared decision making is especially critical in the management of complex arrhythmia problems in LVAD recipients. This Scientific Statement will likely serve as an important springboard for future multi-center, collaborative clinical trials that can allow us to deliver better care for our patients with LVADs.