Continuous-Flow and Pulsatile LVADs
Continuous-flow LVADs were used in 94 (44.1%) of all patients included in this study. Pulsatile-flow LVADs were used in 119 patients (55.9%; Table 1). Four studies used only continuous-flow LVADs, five studies used only pulsatile LVADs, and two studies used a combination of both types (continuous flow used in 55 and 29.2% of the cohort of two studies).
Baseline patient characteristics are summarized in Table 1. The mean age of patients ranged from 28.4 to 50 years, with the male sex predominating in most studies [odds ratio 2.28, p=0.25] (Table 2). Most patients had nonischemic cardiomyopathy, with pooled weighted average proportion of 92.6%, compared with 7.0% of patients having ischemic cardiomyopathy (Figure 2). The mean duration of HF ranged from less than 1 month to 58.3 months, whereas the mean duration of LVAD support ranged from 57 to 606 days. Preimplant mean LVEF ranged from 12.3% to 22%, whereas mean left ventricular end-diastolic diameter (LVEDD) ranged from 53 to 74.3 mm. Mean Fick cardiac index ranged from 1.6 to 2.24 L/min/m2.
Risk of Bias Assessment
Supplemental Table 1 (see Supplemental Digital Content 1, http://links.lww.com/ASAIO/A89) provides detailed information on study appraisal. Because quality scoring is controversial in meta-analyses of observational studies, two reviewers (D.F.Z. and K.P.) independently appraised each article included in our analysis according to a critical review checklist of the Dutch Cochrane Centre proposed by MOOSE. The key points of this checklist include 1) clear definition of study population; 2) clear definition of outcomes and outcome assessment; 3) independent assessment of outcome parameters; 4) sufficient duration of follow-up; 5) no selective loss during follow-up; and 6) important confounders and prognostic factors identified.
Assessment of Mortality
From all included studies, the perioperative mortality rate ranged from 0% to 22.7%, with weighted pooled mean of 9.2% (95% CI, 5.0–14.5%; I2 = 0). Subgroup analysis revealed that the pooled perioperative mortality was comparable in studies that used continuous-flow LVADs compared with pulsatile LVADs (5.1 vs. 10.9%, p = 0.285; Figure 3 and Table 5). The overall rate of late mortality ranged from 0% to 40%, with weighted pooled mean of 15% (95% CI, 9.0–22.1%; I2 = 31%). Subgroup analysis revealed that the pooled late mortality was not significantly different in continuous-flow LVADs compared with pulsatile LVADs (9.1 vs. 16.5%, p = 0.267; Figure 3 and Table 5).
The overall rate of cardiovascular deaths was 10.8% (95% CI, 4.6–19.2%; I2 = 40.4%), with a range of 0–22.2%. The stroke rate ranged from 0% to 20%, with weighted pooled mean of 4.9% (95% CI, 1.4–10.5; I2 = 23.7%). The rate of postexplant infection ranged from 2.2% to 20%, with weighted pooled mean of 4.3% (95% CI, 1.6–8%; I2 = 0; Figure 3). When analyzed based on type of LVAD, the overall rate of cardiovascular deaths, stroke rate, and postexplant infection had a trend of being lower in the studies that used continuous-flow LVADs compared with pulsatile LVADs (4.5 vs. 7.1%; 11.2 vs. 20%, and 3.7 vs. 6.8%, respectively; Figure 3 and Table 5); however, this did not reach statistical significance.
Recurrence of HF
The recurrence of HF occurred in 0–59.1% of patients, with weighted pooled mean of 18.7% (95% CI, 8.6–31.7%). There was significant heterogeneity between the studies (I2 = 76.8, p < 0.001). However, subgroup analysis revealed that the pooled recurrence of HF was lower in the studies that used continuous-flow LVADs compared with pulsatile LVADs (6.6 vs. 28.3%, p = 0.03). There was no significant heterogeneity for the studies with continuous-flow LVADs (I2 = 0%, p = 0.41); however, significant heterogeneity was present for the studies that used pulsatile LVADs (I2 = 75.3%, p < 0.007; Table 3 and Figure 4). The total number of explants was 205, given an explant rate of 4.98% (range 1.8%–23.5%). When this was analyzed in subgroups, the continuous device group had an explant rate of 2.9% compared to 6.0% in the pulsatile device group.
LVAD Reimplantation and Heart Transplantation
Patients requiring LVAD reimplantation ranged from 0% to 40%, with weighted pooled mean of 8.9% (95% CI, 1.4–20.1%; I2 = 67.2%). The overall risk of patients requiring transplantation after LVAD explantation was 11.2% (95% CI, 4.4–20.1%; I2 = 51.1%), with a range of 0–33% (Table 3 and Figure 4). When analyzed based on the type of LVAD, the rate of patients requiring LVAD reimplantation was substantially lower in the studies that used continuous-flow compared with pulsatile (7.5 vs. 37%, p = 0.001; Figure 3 and Table 5). There was also a trend for higher heart transplantation rates in the pulsatile versus continuous-flow LVAD subgroup (13.9 vs. 4.8%, p = 0.126); however, this difference did not reach statistical significance.
Assessment of Cardiac Function and Long-Term Survival
In terms of LVEF, the pooled preexplantation, early postexplantation, and late postexplantation values were 49% (95% CI, 45.7–52.3%; I2 = 59%; range, 46.9–56.3%), 47.3% (95% CI, 45.4–49.3%; I2 = 0; range, 45.6–58.5%), and 41.2% (95% CI, 34.7–47.7; I2 = 94.8%; range, 24–57.4%), respectively. Subgroup analysis revealed that the pooled preexplantation, early postexplantation, and late postexplantation LVEDD for the studies that used only continuous-flow LVADs were 51.8, 45.6, and 41.5 mm, respectively. Late postexplantation LVEF was found to be significantly higher in the continuous-flow LVAD versus pulsative LVAD (41.5 vs. 24%, p = 0.001).
In terms of LVEDD, the overall preexplantation value was 45.2 mm (95% CI, 36.3–54.1 mm; I2 = 85.1%), with a range of 40.3–49.4 mm. The postexplantation weighted pooled mean LVEDD was 54 mm (95% CI, 50.4–57.6 mm; I2 = 85.0; p < 0.001), with a range of 50–59.4 mm (Figure 5). Subgroup analysis revealed that the pooled preexplantation and postexplantation LVEDD for continuous-flow LVADs were 45.2 and 52.4 mm, respectively. Only one study reported the postexplant LVEDD with a pulsatile LVAD (52 mm).20 The pooled 1, 5, and 10 year survival was 91 (89.9–100%), 76 (71.4–85%), and 65.7%, respectively (Table 3).
The results of this systematic review show encouraging safety and long-term survival outcomes for the use of LVAD as a BTR treatment in carefully selected patients. Pooled meta-regression of the current literature demonstrated that LVAD explantation had a perioperative mortality of 9.2% and late mortality of 15%, with the main cause of death because of HF or other cardiac causes (10.8%). Pooled postweaning 5 year freedom from HF recurrence reached 81.3%. Pooled 1, 5, and 10 year survival rates after the removal of a LVAD were 91, 76, and 65.7%, respectively.
Mechanisms of Left Ventricular Recovery
Several reasons have been hypothesized to explain the mechanism behind how LVAD allows cardiac recovery enabling explantation without heart transplantation. Because of the different proportion of patients who recover, and the speed of recovery between the different etiologies of myocardial disease, the recovery mechanisms are likely to vary. A proportion of patients with dilated cardiomyopathy can achieve recovery of ventricular function after several months of LVAD support.11,21 It is suggested that this is because of reverse remodeling during chronic left ventricular unloading with a LVAD, where cardiac structure is normalized and chamber enlargement is reversed.22,23 Studies have also identified evidence of improvements in myocyte structure and function, as well as favorable reductions in the levels of neurohormones and cytokines in response from LVAD support.10,22,24–26 Conversely, reports have shown that severe acute myocarditis and noncoronary shock can completely reverse after weeks to months of LVAD support.27–30 This has been suggested to be because of the utility of the LVAD to provide the circulatory requirements of the body and improve coronary flow for the time necessary for natural resolution of the disease process or burn out of the inflammatory process.31
Incidence and Predictors of Recurrent Heart Failure After LVAD Explantation
In this review, pooled postexplant freedom from HF recurrence reached 81.3%. Because HF is the most frequent complication after LVAD removal and cause of mortality, several studies have attempted to identify predictors of postweaning cardiac stability and HF recurrence. Dandel et al.8 identified the highest predictive values for >5 year cardiac stability, reporting a LVEF ≥45% with a LVEDD ≤55 mm at a LVAD-off test. This was the largest study included in this review, which evaluated 47 patients with chronic cardiomyopathy who had a 5 and 10 year survival postexplantation of 71.4 and 65.7%, respectively. Postweaning 5 year freedom from HF recurrence was 66%. However, very few patients could fulfill these full-recovery criteria (e.g., only 5.1% [7 of 137] in the study by Saito et al.9). Saito et al. aggressively explanted the LVAD devices in patients with partial cardiac recovery. Saito et al.9 achieved a success rate of LVAD weaning in the partially recovered patients of 50%, and 3 of the 6 patients suffered from recurrence of HF. This was an appropriate success rate considering the overall 5 year freedom from HF recurrence of 66% for the Berlin group.8 Furthermore, Saito et al.9 succeeded in delaying the timing of heart transplantation in two patients for 22 and 42 months.
These findings and the pooled results from this review also highlight that LVAD explantation is feasible in patients without complete recovery of cardiac function.8,12,32 In this review, pooled postweaning 5 year freedom from HF recurrence reached 81.3%, despite the mean pooled preexplantation LVEF being only 49%. Frazier et al. demonstrated that patients who had progressed to a state of compensated HF could undergo explantation safely. One postexplant patient consistently had an ejection fraction of 30–40% and continued to be maintained on conventional medical therapy 6 years after device removal.12
Survival After LVAD Explant Compared with Transplantation
The outcome postexplantation for myocardial recovery is comparable, if not better, survival and lower failure rates and a lower rate of long-term complications than after BTT. Farrar et al.3 demonstrated identical 1 and 5 year survival between the explanted group and the transplanted group (86 vs. 86% and 77 vs. 77%, respectively). In the long term, the transplanted patients encountered typical complications related to their immunosuppression such as hypertension, dyslipidemia, coronary disease, and malignancy. Furthermore, Dandel et al.8 demonstrated that with the option of heart transplantation, 72.7% of patients who were weaned from LVADs were alive at the end of 5th postweaning year (79.2% with their native hearts). This survival is better than that expected after a heart transplant.33 In addition, studies have demonstrated that a significant number of explanted patients achieve a good quality of life without requiring a device or heart transplant.7,34 These findings suggest that the recovery of the native heart, which can take weeks to months of LVAD support, is the most desirable clinical outcome and should be actively sought, with transplantation used only after recovery of ventricular function has been ruled out. This is particularly important in young patients who are unlikely to live a normal lifespan even after a successful heart transplant.
Selection Criteria for Explantation and Assessments for Myocardial Recovery
It is important to highlight that these outcomes after explantation were a result of a regular assessments for myocardial recovery and various selection criteria to determine those patients suitable for LVAD explantation. Birk et al. performed echocardiography with the LVAD turned off for 5, 10, and 15 minutes. If this was well tolerated, the echocardiogram would be repeated after a “6 minute walk” with the device turned off. If a 6 minute walk distance of 300 m was achieved with no deterioration in echo parameters, exercise capacity would be determined with the device off after an appropriate period of rest (>6 hours). MUGA scans were used to assess the LVEF and right ventricular ejection fraction and response to exercise with the LVAD turned off.
After the investigations for myocardial recovery, the decision to explant remains difficult because of the lack of standardized criteria. For example, Birks et al.35 considered LVAD explantation if, with the device off, ventricular dimensions were normalized, LVEF was ≥45%, left ventricular end-diastolic pressure was ≤8 mmHg, cardiac index >2.8, VO2 max ≥20, and VE/VCO2 <34. In comparison, Dandel et al.36 considered weaning if the LVEF was ≥45%, LVEDD ≤ 55mm, cardiac index >2.6, pulmonary artery wedge pressure <13 mmHg, brachial artery pressure ≥65 mmHg, and heart rate <90 beats per minute when the patient was at rest. These variations in criteria likely account for the heterogeneity across studies. Future long-term studies with larger cohorts will be necessary to determine the relevant criteria to optimize patient outcomes.
Combination Program to Maximize Myocardial Recovery
Another potential confounder may be the differences in adjuvant pharmacologic therapy used to promote myocardial recovery before explantation.36,37 Birks and coworkers proposed a combination therapy that aggressively promoted myocardial recovery in patients with advanced dilated cardiomyopathy on LVAD support using a combination of additional specific drug therapies,38–41 combined with close monitoring42,43 of underlying myocardial function with the LVAD turned off or at very low speeds, which resulted in device explantation in several patients.35,44 The rationale of combination therapy is to achieve maximum loading of the myocardium combined with pharmacologic therapy, aimed at reversal of remodeling. It has been suggested that combining LVADs with β-blockers, angiotensin-converting-enzyme inhibitors and angiotensin-1 receptor antagonists, and spironolactone may maximize reverse remodeling through the effects on the renin-angiotensin system, endothelial function, and sarcoplasmic reticulum.45–47 In addition, Yacoub and coworkers40 suggested using an active exercise program and the β2 agonist clenbuterol to induce skeletal muscle hypertrophy, improve performance, and stimulate physiologic myocardial hypertrophy.41,48
Do Outcomes Differ Between Continuous-Flow Versus Pulsatile LVADs?
It is believed that pulsatile LVADs achieve higher coronary flow compared with continuous-flow LVADs, which may result in higher rates of myocardial recovery.49,50 Kato et al. 51 studied the changes in markers of myocardial recovery: left ventricular ejection fraction, mitral E:EЈ ratio, and serum levels of molecular markers (BNP, MMP-9, and TIMP-4) in 61 patients supported with LVADs as bridge to transplant. Thirty-one of these patients were supported with pulsatile LVADs (29 with HeartMate XVE [Thoratec Corp., Pleasanton, CA] and 2 with Thoratec PVAD, [Thoratec Corp., Pleasanton, CA]) and 30 patients with continuous-flow LVADs (27 with HeartMate II [Thoratec Corp., Pleasanton, CA], 2 with Durahart [TerumoHeart, Ann Arbor, MI], and 1 with DeBakey VAD [Houston, TX]). On the basis of improved marker levels, authors concluded that pulsatile-flow LVADs are more effective in inducing myocardial recovery; however, none of the patients were actually explanted to allow analysis of the actual recovery or freedom from recurrence of HF. Krabatsch et al.52 studied 387 patients with dilated cardiomyopathy who underwent LVAD placement at their institution and were able to explant 34 (8.8%) patients in this patient category and found 3 times higher likelihood of explant in patients supported with pulsatile LVADs. The authors suggested that either pulsatility itself or the difference in left ventricular unloading may play a role in this difference.
Although in the study by Kato et al. no patient was actually explanted to study whether the patients have really recovered, in the study by Krabatsch et al.,52 all patients had dilated cardiomyopathy, which may not be representative of the entire patient population who requires LVAD support. Other studies on possible advantage of improved coronary flow in LVAD patients are either based on small number of animal models50 or in vitro.49 Overall, the published results in the literature are hypothesis generating but not sufficient to show the advantage of pulsatile LVADs in increasing the likelihood of explant.
Our analysis also suggested that pulsatile pumps got explanted more often than continuous-flow pumps, but the difference was not statistically significant (6.0% vs 2.9%, p=0.12). Shorter life and higher complication profiles of these pumps may factor indirectly in the decision to explant. Conversely, our pooled analysis of all published data identified that explantation from continuous-flow LVADs had low rates of HF recurrence (6.6 vs. 28.3%), LVAD reimplantations (7.5 vs. 37%), and heart transplants (4.8 vs. 13.9%) compared with pulsatile LVADs. Late post-explantation LVEF was significantly higher in the continuous-flow LVAD versus pulsatile LVAD subgroup (41.5 vs. 24%, p = 0.001). Given these findings, it could be possible that patients with pulsatile LVADs are more likely to get explanted; however, they are also more likely to get recurrence of HF and require LVAD reimplantation compared with continuous-flow LVADs. There was also a trend for higher heart transplantation rates in the pulsatile versus continuous-flow LVAD subgroup (13.9 vs. 4.8%, p = 0.126), which could have contributing to higher explant rates in pulsatile LVAD patients. Given too much heterogeneity in the pulsatile LVAD group, however, these differences should be interpreted with caution.
In further attempt to enhance the myocardial recovery, currently, flow modulation control strategies are being examined to generate pulsatility in centrifugal continuous-flow LVADs. For example, the new HeartMate III LVAD (Thoratec Corp.) includes a pulse mode that can produce near-physiologic pulse pressure,53 whereas the HeartWare HVAD (HeartWare Inc., Framinham, MA) speed modulating function, intended to avoid thrombus formation, is currently being further developed to induce greater pulsatility.54 Although strengths of the present systematic review include a pooled meta-analysis of the data from all currently available literature, as well as subgroup analysis according to LVAD device type, future large randomized controlled trials involving newer LVADs are warranted to shed more light at the outcomes after LVAD explantation.
The clinical implications of LVAD explantation are significant considering the risks associated with LVAD therapy (i.e., infection, device failure), in addition to the increasing number of patients with HF paired with the limited number of donor hearts available for transplantation. Moreover, although the proportion of patients suitable for explantation is widely believed to be low, the true number of patients who are suitable to undergo explantation is not actually known as LVAD centers do not to actively pursue a reconditioning strategy. Birks et al.7 have demonstrated that aggressively attempting recovery in patients in a bridge-to-transplant program can avoid transplantation in a significant proportion. Therefore, to achieve larger, more reliable studies, as well as ease the demand for donor hearts, LVAD centers need to vigorously assess whether patients in the bridge-to-transplant program are viable to undergo explantation.8
Future Research and Improvement for LVAD Explantation
For LVADs to be used routinely as a BTR and as viable alternative to cardiac transplantation, further clarification as to which patients have the best possibility of recovering ventricular function with LVADs is warranted. Also, optimal modalities of support, appropriate adjuvant medical therapies, and other appropriate weaning strategies need to be developed. Some authors have suggested that full left ventricular pressure unloading for periods of time should be implemented to encourage stretch-mediated reverse remodeling.3 Others have suggested a strategy of combined mechanical and pharmacologic therapy to stimulate physiologic hypertrophy during LVAD support.55 Moreover, there has been increasing interest in the use of stem cell therapy to synergistically enhance LVAD-mediated cardiac recovery (ongoing trials by Cardiothoracic Surgical Trials Network http://www.ctsurgerynet.org)
Interpretation of the results from this review needs to take into consideration several limitations. First, there were only a small number of patients in the included studies. This restricted additional statistical evaluation based on the etiology of disease and also reduced statistical power of analysis. Second, there was a paucity of data regarding the change of LVEF and LVEDD over time and essential absence of other parameter such as stroke volume. This makes it difficult to assess the change of cardiac function after LVAD explant.
The results of this systematic review of LVAD patients show encouraging safety and long-term survival outcomes using a bridge-to-recovery treatment option as a competitive strategy since outcomes exceed that documents for heart transplant. Recovery of ventricular function should be actively sought in LVAD centers, using aggressive recondition methods, leaving transplantation for patients which sufficient recovery does not occur.
1. Lloyd-Jones D, Adams RJ, Brown TM, et al: Heart disease and stroke statistics—2010 update: A report from the American Heart Association. Circulation 2010.121: e46–e215.
2. McMurray JJ, Petrie MC, Murdoch DR, Davie AP: Clinical epidemiology of heart failure: Public and private health burden. Eur Heart J 1998.19 (suppl P): P9–P16.
3. Farrar DJ, Holman WR, McBride LR, et al: Long-term follow-up of Thoratec ventricular assist device bridge-to-recovery patients successfully removed from support after recovery of ventricular function. J Heart Lung Transplant 2002.21: 516–521.
4. Miller LW, Pagani FD, Russell SD, et al; HeartMate II Clinical Investigators: Use of a continuous-flow device in patients awaiting heart transplantation. N Engl J Med 2007.357: 885–896.
5. Slaughter MS, Rogers JG, Milano CA, et al; HeartMate II Investigators: Advanced heart failure treated with continuous-flow left ventricular assist device. N Engl J Med 2009.361: 2241–2251.
6. Pagani FD, Miller LW, Russell SD, et al; HeartMate II Investigators: Extended mechanical circulatory support with a continuous-flow rotary left ventricular assist device. J Am Coll Cardiol 2009.54: 312–321.
7. Birks EJ, George RS, Firouzi A, et al: Long-term outcomes of patients bridged to recovery versus patients bridged to transplantation. J Thorac Cardiovasc Surg 2012.144: 190–196.
8. Dandel M, Weng Y, Siniawski H, Potapov E, Lehmkuhl HB, Hetzer R: Long-term results in patients with idiopathic dilated cardiomyopathy after weaning from left ventricular assist devices. Circulation 2005.112 (9 suppl): I37–I45.
9. Saito S, Toda K, Miyagawa S, et al: Hemodynamic changes during left ventricular assist device-off test correlate with the degree of cardiac fibrosis and predict the outcome after device explantation. J Artif Organs 2015.18: 27–34.
10. Frazier OH, Benedict CR, Radovancevic B, et al: Improved left ventricular function after chronic left ventricular unloading. Ann Thorac Surg 1996.62: 675–681; discussion 681–682.
11. Frazier OH, Myers TJ: Left ventricular assist system as a bridge to myocardial recovery. Ann Thorac Surg 1999.68: 734–741.
12. Frazier OH, Baldwin ACW, Demirozu ZT, et al: Ventricular reconditioning and pump explantation in patients supported by continuous-flow left ventricular assist devices. J Heart Lung Transplant 2015.34: 766–772.
13. Goldstein DJ, Maybaum S, MacGillivray TE, et al; HeartMate II Clinical Investigators: Young patients with nonischemic cardiomyopathy have higher likelihood of left ventricular recovery during left ventricular assist device support. J Card Fail 2012.18: 392–395.
14. Lamarche Y, Kearns M, Josan K, et al: Successful weaning and explantation of the Heartmate II left ventricular assist device. Can J Cardiol 2011.27: 358–362.
15. Dandel M, Weng Y, Siniawski H, et al. Heart failure reversal by ventricular unloading in patients with chronic cardiomyopathy: criteria for weaning from ventricular assist devices.Eur Heart J 2011.32: 1148–1160.
16. Mancini DM, Beniaminovitz A, Levin H, et al: Low incidence of myocardial recovery after left ventricular assist device implantation in patients with chronic heart failure. Circulation 1998.98: 2383–2389.
17. Maybaum S, Mancini D, Xydas S, et al; LVAD Working Group: Cardiac improvement during mechanical circulatory support: A prospective multicenter study of the LVAD Working Group. Circulation 2007.115: 2497–2505.
18. Simon MA, Primack BA, Keuteberg J, et al: Left ventricular remodeling and myocardial recovery on mechanical circulatory support. J Card Fail. 2010.16: 99–105.
19. Tchantchaleishvili V, Cheyne C, Sherazi S, et al: Single-Center Experience With HeartMate II Left Ventricular Assist Device Explantation. Artificial Organs [epub ahead of print].
20. Mancini DM, Beniaminovitz A, Levin H, et al: Low incidence of myocardial recovery after left ventricular assist device implantation in patients with chronic heart failure. Circulation 1998.98: 2383–2389.
21. Hetzer R, Müller J, Weng Y, Wallukat G, Spiegelsberger S, Loebe M: Cardiac recovery in dilated cardiomyopathy by unloading with a left ventricular assist device. Ann Thorac Surg 1999.68: 742–749.
22. Levin HR, Oz MC, Chen JM, Packer M, Rose EA, Burkhoff D: Reversal of chronic ventricular dilation in patients with end-stage cardiomyopathy by prolonged mechanical unloading. Circulation 1995.91: 2717–2720.
23. Madigan JD, Barbone A, Choudhri AF, et al: Time course of reverse remodeling of the left ventricle during support with a left ventricular assist device. J Thorac Cardiovasc Surg 2001.121: 902–908.
24. Young JB: Healing the heart with ventricular assist device therapy: Mechanisms of cardiac recovery. Ann Thorac Surg 2001.71 (3 suppl): S210–S219.
25. Grigore A, Poindexter B, Vaughn WK, et al: Alterations in alpha adrenoreceptor density and localization after mechanical left ventricular unloading with the Jarvik flowmaker left ventricular assist device. J Heart Lung Transplant 2005.24: 609–613.
26. Torre-Amione G, Loebe M: Frazier OH, Kirklin JK, Myocardial recovery following prolonged mechanical support. ISHLT Monograph Series. Mechanical Circulatory Support, 2006, Volume 1. 155–169In .
27. Chen JM, Spanier TB, Gonzalez JJ, et al: Improved survival in patients with acute myocarditis using external pulsatile mechanical ventricular assistance. J Heart Lung Transplant 1999.18: 351–357.
28. Dembitsky WP, Moore CH, Holman WL, et al: Successful mechanical circulatory support for noncoronary shock. J Heart Lung Transplant 1992.11 (1 pt 1): 129–135.
29. Houël R, Vermes E, Tixier DB, Le Besnerais P, Benhaiem-Sigaux N, Loisance DY: Myocardial recovery after mechanical support for acute myocarditis: Is sustained recovery predictable? Ann Thorac Surg 1999.68: 2177–2180.
30. Ueno T, Bergin P, Richardson M, Esmore DS: Bridge to recovery with a left ventricular assist device for fulminant acute myocarditis. Ann Thorac Surg 2000.69: 284–286.
31. Rose EA, Frazier OH: Resurrection after mechanical circulatory support. Circulation 1997.96: 393–395.
32. Müller J, Wallukat G, Weng YG, et al: Weaning from mechanical cardiac support in patients with idiopathic dilated cardiomyopathy. Circulation 1997.96: 542–549.
33. Taylor DO, Edwards LB, Boucek MM, et al: Registry of the International Society for Heart and Lung Transplantation: Twenty-fourth official adult heart transplant report—2007. J Heart Lung Transplant 2007.26: 769–781.
34. George RS, Yacoub MH, Bowles CT, et al: Quality of life after removal of left ventricular assist device for myocardial recovery. J Heart Lung Transplant 2008.27: 165–172.
35. Birks EJ, Tansley PD, Hardy J, et al: Left ventricular assist device and drug therapy for the reversal of heart failure. N Engl J Med 2006.355: 1873–1884.
36. Dandel M, Weng Y, Siniawski H, et al: Prediction of cardiac stability after weaning from left ventricular assist devices in patients with idiopathic dilated cardiomyopathy. Circulation 2008.118 (14 suppl): S94–S105.
37. Komoda T, Komoda S, Dandel M, Weng Y, Hetzer R: Explantation of INCOR left ventricular assist device after myocardial recovery. J Card Surg 2008.23: 642–647.
38. Soppa GK, Smolenski RT, Latif N, et al: Effects of chronic administration of clenbuterol on function and metabolism of adult rat cardiac muscle. Am J Physiol Heart Circ Physiol 2005.288: H1468–H1476.
39. Petrou M, Clarke S, Morrison K, Bowles C, Dunn M, Yacoub M: Clenbuterol increases stroke power and contractile speed of skeletal muscle for cardiac assist. Circulation 1999.99: 713–720.
40. Petrou M, Wynne DG, Boheler KR, Yacoub MH: Clenbuterol induces hypertrophy of the latissimus dorsi muscle and heart in the rat with molecular and phenotypic changes. Circulation 1995.92 (9 suppl): II483–II489.
41. Wong K, Boheler KR, Bishop J, Petrou M, Yacoub MH: Clenbuterol induces cardiac hypertrophy with normal functional, morphological and molecular features. Cardiovasc Res 1998.37: 115–122.
42. George RS, Sabharwal NK, Webb C, et al: Echocardiographic assessment of flow across continuous-flow ventricular assist devices at low speeds. J Heart Lung Transplant 2010.29: 1245–1252.
43. George RS, Yacoub MH, Tasca G, et al: Hemodynamic and echocardiographic responses to acute interruption of left ventricular assist device support: Relevance to assessment of myocardial recovery. J Heart Lung Transplant 2007.26: 967–973.
44. Birks EJ, George RS, Hedger M, et al: Reversal of severe heart failure with a continuous-flow left ventricular assist device and pharmacological therapy: A prospective study. Circulation 2011.123: 381–390.
45. Pitt B, Zannad F, Remme WJ, et al: The effect of spironolactone on morbidity and mortality in patients with severe heart failure. Randomized Aldactone Evaluation Study Investigators. N Engl J Med 1999.341: 709–717.
46. Pitt B: Regression of left ventricular hypertrophy in patients with hypertension: blockade of the renin-angiotensin-aldosterone system. Circulation 1998.98: 1987–1989.
47. McKelvie RS, Yusuf S, Pericak D, et al: Comparison of candesartan, enalapril, and their combination in congestive heart failure: Randomized evaluation of strategies for left ventricular dysfunction (RESOLVD) pilot study. The RESOLVD Pilot Study Investigators. Circulation 1999.100: 1056–1064.
48. Wong K, Boheler KR, Petrou M, Yacoub MH: Pharmacological modulation of pressure-overload cardiac hypertrophy: Changes in ventricular function, extracellular matrix, and gene expression. Circulation 1997.96: 2239–2246.
49. Giridharan GA, Ewert DL, Pantalos GM, et al: Left ventricular and myocardial perfusion responses to volume unloading and afterload reduction in a computer simulation. ASAIO J 2004.50: 512–518.
50. Ootaki Y, Kamohara K, Akiyama M, et al: Phasic coronary blood flow pattern during a continuous flow left ventricular assist support. Eur J Cardiothorac Surg 2005.28: 711–716.
51. Kato TS, Chokshi A, Singh P, et al: Effects of continuous-flow versus pulsatile-flow left ventricular assist devices on myocardial unloading and remodeling. Circ Heart Fail 2011.4: 546–553.
52. Krabatsch T, Schweiger M, Dandel M, et al: Is bridge to recovery more likely with pulsatile left ventricular assist devices than with nonpulsatile-flow systems? Ann Thorac Surg 2011.91: 1335–1340.
53. Bourque K, Gernes DB, Loree HM II, et al: HeartMate III: Pump design for a centrifugal LVAD with a magnetically levitated rotor. ASAIO J 2001.47: 401–405.
54. Larose JA, Tamez D, Ashenuga M, Reyes C: Design concepts and principle of operation of the HeartWare ventricular assist system. ASAIO J 2010.56: 285–289.
55. Yacoub MH: A novel strategy to maximize the efficacy of left ventricular assist devices as a bridge to recovery. European Heart J 2001.7: 534–540.
ventricular recondition; pump explantation; left ventricular assist devices; review
Supplemental Digital Content
Copyright © 2016 by the American Society for Artificial Internal Organs