The Centers for Disease Control and Prevention estimate that in the last two decades, the prevalence of obesity in the U.S. (body mass index [BMI] ≥30 kg/m²) has increased from 23% to 35% (approximately 79 million adults, 20 years and older), with 6.4% of individuals identified as extremely obese (BMI ≥35 kg/m²).¹ Specific adverse cardiovascular effects of obesity include hypertension, diabetes/metabolic syndrome, coronary heart disease, systolic and diastolic heart failure, atrial fibrillation, and pulmonary hypertension.²

From a hemodynamic perspective, increased total blood volume and cardiac output associated with obesity manifests as chronically elevated cardiovascular workload, which may result in chamber dilatation and eccentric hypertrophy, precipitate systolic and diastolic heart failure and atrial fibrillation. From a hormonal perspective, increased levels of leptin and C-reactive protein are associated with a pro-thrombotic, inflammatory state and increased cardiovascular events.² Taken together, the "cardiomyopathy of obesity" may result in end-stage heart failure requiring consideration of advanced therapies. In the Framingham Heart Study, after adjustment of established risk factors for heart failure, a one-point increment in BMI was associated with a 5% increased risk of heart failure in men and a 7% increase in women.³

Importantly, while obesity may soon become the leading cause of preventable death, there is increasing data that advanced heart failure patients may have a survival advantage over heart failure patients with a lower BMI.⁴ In the Acute Decompensated Heart Failure National Registry (ADHERE) of patients hospitalized for acute decompensated heart failure, higher BMI was associated with lower mortality, with every five-point increase in BMI associated with a 10% mortality reduction.⁵ In other studies, a U-shaped mortality curve is more commonly seen, with extremes of BMI associated with increased mortality and survival advantage in the mid-range overweight-obese cohorts.^6,7 Thus the "obesity paradox" suggests that cardiovascular disease, and specifically heart failure, survival may be more favorable in the mid-range obese cohorts as compared to non-obese patients. With a rapidly increasing prevalence of this demographic, a critical analysis of the risks and benefits of advanced therapeutic options for end-stage heart failure is essential.

Obesity is an important relative contraindication to heart transplantation, with multiple reports of poor outcomes linked to long wait times related to identifying appropriately size-matched donors, perioperative sternal wound infections, and longer-term morbidity related to uncontrolled hypertension and diabetes.^8,9 Many centers use the cut-off of BMI ≥35 kg/m² for transplant ineligibility. Given the limited donor pool, heart transplantation may be considered a scarce resource with intended allocation to only those recipients who may have the best possible outcomes.

In contrast, mechanical circulatory support, while also intended only for those patients with the best possible outcome, may be considered "less scarce" in relative terms. As either bridge to transplant (BTT), or as destination therapy (DT) for those patients ineligible for heart transplantation, the issue of the status of the obese patient in the context of MCS is a controversial topic. One early multicenter study of 222 patients who underwent implantation of the Novacor LVAD device showed no significant impact of BMI on outcome.¹⁰ Another single-center study of 590 patients undergoing VAD therapy (multiple device types) showed that while there was an increase in a combined endpoint of 30-day mortality or failure of procedural success in patients with a BMI of ≥35 kg/m², there were no significant differences in the survival alone at 30 days, one year, and five years between BMI categories.¹¹

While initial studies of currently approved continuous flow LVAD devices have generally tended to exclude patients with a BMI ≥40 kg/m^2,12,13 post-approval studies suggest that these devices can safely be implanted in obese patients without prohibitively increased operative risk. Coyle et al. reported outcomes in patients implanted with an LVAD as DT comparing those with BMI >30 with those with BMI <30, including many with a HeartMate II device, and found no difference in one-year survival between the two groups (P >0.5).¹⁴ Yanagida et al. reported on outcomes after device implantation at their center in obese patients (BMI >30), and also found no significant difference in one-year survival as compared to non-obese patients with devices implanted during the same period.¹⁵ Furthermore, a post-hoc analysis of the 896 combined BTT and HeartMate II DT trial patients, including 196 obese and 88 extremely obese patients, found that BMI was not associated with worse survival, although there was an increase in device-related infection between patients with a normal BMI (<30) vs. extremely obese (≥35) (24% vs. 35%, p = 0.04).¹⁶ Indeed, there was a statistically significant increase in driveline infections or sepsis in the HeartWare Ventricular Assist Device (HVAD) Bridge to Transplant ADVANCE trial in patients with higher BMI, although the cut point was 29.4 versus 27.6 BMI (p = 0.015), although no differences in survival in the driveline infection cohort. Importantly, there was no mandated driveline management protocol in the ADVANCE trial.

Driveline or other device-related infections are not trivial and require increased attention on the care of the obese patient. This is particularly important for patients who gain weight after the VAD has been placed. Importantly, while there was some initial success of weight loss in patients implanted with the pulsatile HeartMate XVE LVAS pump,¹⁵ further studies in obese patients implanted with modern era continuous flow LVAD devices have unfortunately found weight loss to be minimal in most patients.^17,18 This has generally been the case at the authors' center as well.

However, LVAD support in these patients does provide hemodynamic support for select motivated patients to continue in efforts to lose weight, especially in those who could otherwise be transplant candidates. In selected cases, bariatric surgery is a viable option to achieve weight loss. Chaudhry et al. reported a case series of successful sleeve gastrectomies in six patients with end-stage heart failure and morbid obesity, three of whom were supported with a HeartMate II LVAD, with sufficient weight loss in all of them to achieve candidacy for heart transplantation at their center.¹⁹

Thus, while the care of obese patients with heart failure is clearly more complicated, evidence exists that obese patients can safely undergo LVAD implantation without excessive perioperative risk with equivalent one-year survival to their non-obese counterparts. Greater care must be taken to prevent device complications in these patients, such as driveline infections, but in conjunction with aggressive weight loss strategies that may include bariatric surgery, weight loss may be possible. With the rapidly expanding demographic of the obese patient with end-stage heart failure, a critical re-appraisal of VAD eligibility and special management considerations seems inevitable.

References

1. U.S. Department of Health and Human Services. Division of Nutrition, Physical Activity and Obesity, National Center for Chronic Disease Prevention and Health Promotion. Overweigt and Obesity. Data & Statistics (Centers for Disease Control and Prevention website). 2015. Available at: http://cdc.gov/obesity/data. Accessed 5/13/15.
2. Lavie CJ, Milani RV, Ventura HO. Obesity and cardiovascular disease: risk factor, paradox, and impact of weight loss. J Am Coll Cardiol 2009;53:1925-32.
3. Kenchaiah S, Evans JC, Levy D, et al. Obesity and the risk of heart failure. N Engl J Med 2002;347:305-13.
4. Lavie CJ, Mehra MR, Milani RV. Obesity and heart failure prognosis: paradox or reverse epidemiology. Eur Heart J 2005;26:5-7.
5. Fonarow GC, Srikanthan P, Costanzo MR, et al. An obesity paradox in acute heart failure: analysis of body mass index and in-hospital mortality in 108,927 patients in the acute decompensated heart failure national registry. Am Heart J 2007;153:74-81.
6. Khalid U, Ather S, Bavishi C, et al. Pre-morbid body mass index and mortality after incident heart failure: the ARIC Study. J Am Coll Cardiol 2014;64:2743-9.
7. Nagarajan V, Cauthen CA, Starling RC, Tang WHW. Prognosis of morbid obesity patients with advanced heart failure. Congest Heart Fail 2013;19:160-4.
8. Mehra MR, Kobashigawa J, Starling R, et al. Listing criteria for heart transplantation: International Society for Heart and Lung Transplantation guidelines for the care of cardiac transplant candidates--2006. J Heart Lung Transplant 2006;25:1024-42.
9. Cimato TR, Jessup M. Recipient selection in cardiac transplantation: contraindications and risk factors for mortality. J Heart Lung Transplant 2002;21:1161-73.
10. Butler J, Howser R, Portner PM, Pierson RN. Body mass index and outcomes after left ventricular assist device placement. Ann Thorac Surg 2005;79:66-73.
11. Musci M, Loforte A, Potapov EV, et al. Body mass index and outcome after ventricular assist device placement. Ann Thorac Surg 2008;86:1236-42.
12. Miller LW, Pagani FD, Russell SD, et al. Use of a continuous-flow device in patients awaiting heart transplantation. N Engl J Med 2007;357:885-96.
13. Slaughter MS, Rogers JG, Milano CA, et al. Advanced heart failure treated with continuous-flow left ventricular assist device. N Engl J Med 2009;361:2241-51.
14. Coyle LA, Ising MS, Gallagher C, et al. Destination therapy: one-year outcomes in patients with a body mass index greater than 30. Artif Organs 2010;34:93-97.
15. Yanagida R, Czer LSC, Mirocha J, et al. Left ventricular assist device in patients with body mass index greater than 30 as bridge to weight loss and heart transplant candidacy. Transplant Proc 2014;46:3575-9.
16. Brewer RJ, Lanfear DE, Sai-Sudhakar CB, et al. Extremes of body mass index do not impact mid-term survival after continuous-flow left ventricular assist device implantation. J Heart Lung Transplant 2012;31:167-72.
17. Dhesi P, Simsir SA, Daneshvar D, Rafique A, Phan A, Schwarz ER. Left ventricular assist device as "bridge to weight loss" prior to transplantation in obese patients with advanced heart failure. Ann Transplant 2011;16:5-13.
18. Emani S, Brewer RJ, John R, et al. Patients with low compared with high body mass index gain more weight after implantation of a continuous-flow left ventricular assist device. J Heart Lung Transplant 2013;32:31-5.
19. Chaudhry UI, Kanji A, Sai-Sudhakar CB, Higgins RS, Needleman BJ. Laparoscopic sleeve gastrectomy in morbidly obese patients with end-stage heart failure and left ventricular assist device: medium-term results. Surg Obes Relat Dis 2015;11:88-93.

Keywords: Atrial Fibrillation, Bariatric Surgery, Bariatric Surgery, Blood Volume, Body Mass Index, Body Weight, C-Reactive Protein, Cardiac Output, Cardiomyopathies, Centers for Disease Control and Prevention, U.S., Coronary Disease, Diabetes Mellitus, Dilatation, Gastrectomy, Heart Failure, Heart Failure, Diastolic, Heart Transplantation, Heart-Assist Devices, Hemodynamics, Hypertension, Hypertension, Pulmonary, Hypertrophy, Leptin, Metabolic Syndrome, Obesity, Morbid, Overweight, Prevalence, Registries, Risk Assessment, Risk Factors, Sepsis, Weight Loss, Wound Infection

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