Update on Mechanical Circulatory Support in Heart Failure
Update on Mechanical Circulatory Support in Heart Failure
LVADs have been in use as a bridge to heart transplantation for 20 years; the HeartMate XVE device, an electrically powered pulsatile pump, was approved for this purpose in 1994. The Randomised Evaluation of Mechanical Assistance in Treatment of Chronic Heart Failure (REMATCH) study evaluated the long term benefit of HeartMate XVE placement compared with optimal medical treatment in end-stage heart failure patients. The rates of survival at 1 year were 52% in the device group and 25% in the medical treatment group (p=0.002), and at 2 years the survival rates were 23% and 8% (p=0.09), respectively. A 48% reduction in death from all causes was attributable to LVAD treatment compared with best medical treatment in this trial, and on this basis, the HeartMate XVE was approved for use as destination therapy in 2002.
Follow-up studies since REMATCH have shown that uptake of chronic LVAD treatment has been limited because there is an unacceptably high incidence of device failure. In addition, Leitz's work shows that there continues to be a very high early mortality with a continued decline in survival later. Although REMATCH showed that LVAD implantation improved survival compared to medical treatment, both groups had an extremely high early mortality and most were on inotropic support. This underlines the importance of patient selection. In this respect, Leitz and colleagues showed that using a novel operative risk score encompassing severity of heart failure, nutritional status, renal function, and right ventricular (RV) function, the patients with the lowest risk had the best early survival. But, even in the sickest patients, LVAD treatment offered a significant survival advantage, as shown in a subsequent sub-study of the REMATCH population and in a recent study with the Novacor device (also a pulsatile device) in inotrope dependent patients with end-stage heart failure.
Unlike pulsatile pumps, a continuous flow pump based on either axial or centrifugal motors can be made smaller and more durable. They can also be converted easily to a totally implantable system. These types of axial flow devices have been in development since 1988 and were first implanted in clinical trials 10 years later (figures 1 and 2). The advantage of these devices is their smaller size and fewer moving parts, which should increase durability. Concerns about non-physiological non-pulsatile output from these devices resulting in possible end-organ damage have been allayed by recent data showing their safety in relatively long term use as a bridge to transplantation when compared with pulsatile devices. An important issue with axial flow devices is their requirement for anticoagulation and the risk of thrombosis and haemolysis. The most commonly used axial device, the HeartMate II, is already FDA approved for bridge to transplantation. A totally implantable LVAD, the Lionheart device, was approved as destination therapy in Europe. The absence of an external drive-line was thought to significantly reduce the risk of infection. Unfortunately this pump proved to have serious durability problems with the blood sac which tended to rupture, and this only came to light in patients after 1 year. It has now been withdrawn from clinical practice.
In a recently reported randomised trial, Slaughter and colleagues showed that a continuous flow LVAD, HeartMate ll, in patients with advanced heart failure significantly improved the probability of survival free from stroke and device failure at 2 years compared with a pulsatile device. The primary composite end point was survival free from disabling stroke and reoperation to repair or replace the device. This was achieved in more patients with continuous flow than with pulsatile flow devices (62 of 134 (46%) vs 7 of 66 (11%); p<0.001; HR 0.38, 95% CI 0.27 to 0.54; p<0.001), and patients with continuous flow devices had superior actuarial survival rates at 2 years (58% vs 24%, p=0.008). This is a significant achievement, but the risk of stroke, infection and device malfunction remains a reality. In this study 59 of 134 patients (44%) receiving the continuous flow device had a disabling stroke or died within 2 years. While helpful and reliable, LVADs still represent a form of life support with a specific set of burdens and complications.
(Enlarge Image)
Figure 1.
HeartMate II rotary axial impeller pump.
Left Ventricular Assist Devices
LVADs have been in use as a bridge to heart transplantation for 20 years; the HeartMate XVE device, an electrically powered pulsatile pump, was approved for this purpose in 1994. The Randomised Evaluation of Mechanical Assistance in Treatment of Chronic Heart Failure (REMATCH) study evaluated the long term benefit of HeartMate XVE placement compared with optimal medical treatment in end-stage heart failure patients. The rates of survival at 1 year were 52% in the device group and 25% in the medical treatment group (p=0.002), and at 2 years the survival rates were 23% and 8% (p=0.09), respectively. A 48% reduction in death from all causes was attributable to LVAD treatment compared with best medical treatment in this trial, and on this basis, the HeartMate XVE was approved for use as destination therapy in 2002.
Follow-up studies since REMATCH have shown that uptake of chronic LVAD treatment has been limited because there is an unacceptably high incidence of device failure. In addition, Leitz's work shows that there continues to be a very high early mortality with a continued decline in survival later. Although REMATCH showed that LVAD implantation improved survival compared to medical treatment, both groups had an extremely high early mortality and most were on inotropic support. This underlines the importance of patient selection. In this respect, Leitz and colleagues showed that using a novel operative risk score encompassing severity of heart failure, nutritional status, renal function, and right ventricular (RV) function, the patients with the lowest risk had the best early survival. But, even in the sickest patients, LVAD treatment offered a significant survival advantage, as shown in a subsequent sub-study of the REMATCH population and in a recent study with the Novacor device (also a pulsatile device) in inotrope dependent patients with end-stage heart failure.
Unlike pulsatile pumps, a continuous flow pump based on either axial or centrifugal motors can be made smaller and more durable. They can also be converted easily to a totally implantable system. These types of axial flow devices have been in development since 1988 and were first implanted in clinical trials 10 years later (figures 1 and 2). The advantage of these devices is their smaller size and fewer moving parts, which should increase durability. Concerns about non-physiological non-pulsatile output from these devices resulting in possible end-organ damage have been allayed by recent data showing their safety in relatively long term use as a bridge to transplantation when compared with pulsatile devices. An important issue with axial flow devices is their requirement for anticoagulation and the risk of thrombosis and haemolysis. The most commonly used axial device, the HeartMate II, is already FDA approved for bridge to transplantation. A totally implantable LVAD, the Lionheart device, was approved as destination therapy in Europe. The absence of an external drive-line was thought to significantly reduce the risk of infection. Unfortunately this pump proved to have serious durability problems with the blood sac which tended to rupture, and this only came to light in patients after 1 year. It has now been withdrawn from clinical practice.
In a recently reported randomised trial, Slaughter and colleagues showed that a continuous flow LVAD, HeartMate ll, in patients with advanced heart failure significantly improved the probability of survival free from stroke and device failure at 2 years compared with a pulsatile device. The primary composite end point was survival free from disabling stroke and reoperation to repair or replace the device. This was achieved in more patients with continuous flow than with pulsatile flow devices (62 of 134 (46%) vs 7 of 66 (11%); p<0.001; HR 0.38, 95% CI 0.27 to 0.54; p<0.001), and patients with continuous flow devices had superior actuarial survival rates at 2 years (58% vs 24%, p=0.008). This is a significant achievement, but the risk of stroke, infection and device malfunction remains a reality. In this study 59 of 134 patients (44%) receiving the continuous flow device had a disabling stroke or died within 2 years. While helpful and reliable, LVADs still represent a form of life support with a specific set of burdens and complications.
(Enlarge Image)
Figure 1.
HeartMate II rotary axial impeller pump.
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