By Jamie L. W. Kennedy, MD, FACC

Associate Professor, Division of Cardiology, Advanced Heart Failure & Transplant Cardiology, University of California, San Francisco

Dr. Kennedy has no relevant financial relationships with ineligible companies to disclose.

SYNOPSIS: A registry of patients transitioned from extracorporeal life support to durable mechanical circulatory support was used to derive a tool predicting one-year survival.

SOURCE: Saeed D, Potapov E, Loforte A, et al. Transition from temporary to durable circulatory support systems. J Am Coll Cardiol 2020;76:2956-2964.

Using extracorporeal life support (ECLS) to rescue patients in cardiogenic shock has become more popular. Some patients can be weaned from ECLS successfully (e.g., after revascularization or valve intervention). However, patients with severe ventricular dysfunction often cannot be weaned. Thus, treatment options narrow to durable mechanical circulatory support (MCS), heart transplant, or comfort care. There are few data to guide the selection of patients supported by ECLS for durable MCS.

Saeed et al constructed a registry of 531 patients at 11 European centers who transitioned from ECLS to durable MCS between January 2010 and August 2018. There were no centralized protocols regarding ECLS weaning, patient selection for MCS, or timing of MCS implant. Patient data were collected before MCS implant and outcomes collected afterward, including patients who subsequently underwent heart transplantation or device explant.

One-third of patients had undergone CPR before ECLS, and one-third required renal replacement therapy while supported by ECLS. Similar to prior MCS studies, 82% of patients were men, and the average age was 53 years. Cardiomyopathy was ischemic in etiology for 57% of patients, 29% had atrial fibrillation, 25% had undergone cardiac surgery, and 23% had diabetes mellitus. ECLS cannulation was peripheral in 87% of patients, and 25% also had an intra-aortic balloon pump.

Patients were supported by ECLS a median of five days before undergoing MCS implant. Cardiopulmonary bypass was used for 61% of implants. HeartWare HVAD was implanted in 372 patients, HeartMate II LVAD in 81, HeartMate 3 in 44, and small numbers of a variety of other assist devices. The total artificial heart was used for 19 patients. Of those who underwent LVAD implant, 225 also required right ventricular mechanical support, although only seven durable RVADs were implanted. Other postoperative complications included respiratory failure in 48%, renal failure requiring dialysis in 61%, liver failure in 25%, and bleeding requiring re-exploration in 36%.

Survival at 30 days was 77%, one year 53%, and three years 43%. Over a median follow-up of 1.27 years, 21% underwent transplant, and 5% of VADs were explanted for recovery. Stroke was the most common long-term complication at 0.13 events per patient year. There was no comment on the severity of neurological injury.

The authors developed a model predicting survival at one year from patient characteristics available at the time of durable MCS implant, including demographics, comorbidities, lab values, pressor and inotrope doses, prior cardiac surgery, prior CPR, ECLS cannulation strategy, and duration of support. The final model incorporates age, sex, BMI > 30 kg/m2, prior cardiac surgery, lactate level, history of atrial fibrillation, and MELD-XI (model of end-stage liver disease excluding INR) to predict one-year survival. The C index for the model was 0.72. The authors concluded that this model will be useful to help decide who should move from ECLS to durable MCS.

COMMENTARY

As with other registry studies, there were significant limitations. Only patients selected to undergo durable MCS implant were included. The authors did not provide information on patients deemed ineligible for implantation of durable MCS devices. I look forward to validation of the prediction tool in a second patient cohort.

The significantly worse outcomes women experienced in this registry are noteworthy. Using the risk equation, the predicted survival rate for women at one year is 7% less than men in the best of circumstances. The difference approaches 20% with additional risk factors. The data on sex differences in the MCS literature is mixed and limited, since sex-specified outcomes are not reported consistently. The HeartMate II bridge to transplant and HeartMate 3 clinical trials revealed no outcome differences between sexes.1,2 A retrospective study of hospital administration data from seven states revealed significantly worse outcomes for women undergoing implantation of either temporary or durable ventricular assist devices between 1994 and 2012. In-hospital mortality for women was 52.3% vs. 40.8% for men, and the difference remained significant after adjustment for other risk factors.3 A subsequent analysis of the U.S. national inpatient sample between 2009 and 2014, which focused on durable LVADs, revealed similar inpatient mortality for men and women (13.42% and 12.85%, respectively).4 Perhaps most relevant to the Saeed et al article, a recent analysis of the STS-INTERMACS database, which included patients transitioned from ECLS to durable MCS between 2008 and 2017, showed female sex conferred higher mortality.5

If women do experience worse outcomes than men, why? Is sex a surrogate for smaller blood vessels, smaller hearts, or lower muscle mass? Do hormonal differences lead to more thromboembolic complications in women? Do women present with more advanced disease that risk models do not capture adequately? In an environment of increasing financial pressures and scrutiny of outcomes, I fear this unvalidated prediction model will be used to decide candidacy for implantation of durable MCS devices to the detriment of women.

REFERENCES

  1. Boyle AJ, Russell SD, Teuteberg JJ, et al. Low thromboembolism and pump thrombosis with the HeartMate II left ventricular assist device: Analysis of outpatient anticoagulation. J Heart Lung Transplant 2009;28:881-887.
  2. Mehra MR, Uriel N, Naka Y, et al. A fully magnetically levitated left ventricular assist device — final report. N Engl J Med 2019;380:1618-1627.
  3. McIlvennan CK, Lindenfeld J, Kao DP. Sex differences and in-hospital outcomes in patients undergoing mechanical circulatory support implantation. J Heart Lung Transplant 2017;36:82-90.
  4. Briasoulis A, Akintoye E, Mohsen A, et al. Trends in utilization, mortality, major complications, and cost after total artificial heart implantation in the United States (2009-2015). Hellenic J Cardiol 2019; Feb 19;S1109-9666(18)30522-0. doi: 10.1016/j.hjc.2019.02.002. [Online ahead of print].
  5. Arabía FA, Cantor RS, Koehl DA, et al. Interagency registry for mechanically assisted circulatory support report on the total artificial heart. J Heart Lung Transplant 2018;37:1304-1312.