Durability of Continuous-flow LVADs
In total, 1,448 records were identified through electronic searches of the six databases (Figure 1). After screening the articles based on abstract content, 195 full-text publications were assessed according to the selection criteria, and the reference lists were also searched to identify additional relevant articles. Twelve relevant studies were included in the current review, all of which were observational and retrospective (Table 1). Where studies presented separate data for patients receiving continuous- and pulsatile-flow LVADs, only the outcomes for CF-LVADs were included for analysis.
(Enlarge Image)
Figure 1.
Search strategy of systematic review for durability of continuous-flow left ventricular assist devices.
The median sample size was 166 (range, 43–2,816). Three large US multicenter studies were included, as well as data from the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) registry of mechanical assist devices in US patients. Although this may have resulted in some duplication of patients, this was thought to be considerably outweighed by the unique data contributed by each study. Furthermore, two studies included patients as young as 15 years old. However, these studies were still included for analysis as young patients only represented a small proportion of the total sample size.
In one study, LVAD failure was defined as malfunction leading to device exchange or device-related death. In the remaining studies, device failure was defined as malfunction necessitating explantation or replacement.
The baseline demographics are summarized in Table 2. A total of 5,471 patients were included in the present analysis. Of these, 77.7% were male, and the mean weighted age was 54.8 years. Ischemic heart disease was the etiology of cardiac failure in 44.1% of patients. On average, 26.4% of patients were diabetic and 53.3% hypertensive. The CF-LVADs used included the HeartMate II, EVAHEART, Heartware, and Duraheart devices.
The incidence and etiology of device failure is summarized in Table 3. The mean duration of LVAD support was 504.7 days, and the weighted incidence of device failure was relatively low, at 3.9%. For patients with LVAD failure, the average time to device exchange or malfunction was 539.7 days, though this varied greatly (Table 3). The primary etiology of device failure varied considerably amongst the studies, with pump thrombosis being the most common cause overall (50.5% of total device failures). This was followed by lead or cable damage (21.7%), mechanical pump failure (11.6%), device infection (11.1%), and surgical complications associated with the LVAD implantation procedure (2.5%). Other causes of failure reported in one study included unsustained left ventricular recovery following explantation of a pre-existing LVAD (n=1).
Data were interpolated from the competing outcomes and Kaplan-Meier curves of eight studies to approximate long-term rates of device failure and survival with the original LVAD in place. These outcomes are summarized in Table 4. Analysis using weighted means revealed rates of device failure of 0.5%, 1.8%, 2.9%, 4.5% and 6.5% at 2-, 6-, 12-, 18- and 24-months post implantation, respectively. The weighted survival with the original device in place was 90.2% at 2 months, declining to 54.4% at 12 months, and 38.7% at 24 months.
Inspection of the funnel plot (Figure 2) did not show significant asymmetry when overall incidence of device failure was selected as an outcome. Egger's linear regression method suggested that publication bias was not a significant influencing factor (P=0.81520). Trim-and-fill analysis revealed that there were no missing studies, and thus no change in overall effect size was observed. These trends suggest that publication bias did not have a significant influence on the presented analysis.
(Enlarge Image)
Figure 2.
Funnel plot for assessment of publication bias in systematic review for durability of continuous-flow left ventricular assist devices. The logit event rate for device failure (horizontal axis) is presented against the standard error (SE) of the log of logit event rate (vertical axis). The SE inversely corresponds to the study size. Asymmetry of the plot may indicate publication bias. Open circles indicate included studies, while any filled circles (none) would represent imputed studies identified through trim-and-fill analysis.
Results
Quantity and Quality of Evidence
In total, 1,448 records were identified through electronic searches of the six databases (Figure 1). After screening the articles based on abstract content, 195 full-text publications were assessed according to the selection criteria, and the reference lists were also searched to identify additional relevant articles. Twelve relevant studies were included in the current review, all of which were observational and retrospective (Table 1). Where studies presented separate data for patients receiving continuous- and pulsatile-flow LVADs, only the outcomes for CF-LVADs were included for analysis.
(Enlarge Image)
Figure 1.
Search strategy of systematic review for durability of continuous-flow left ventricular assist devices.
The median sample size was 166 (range, 43–2,816). Three large US multicenter studies were included, as well as data from the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) registry of mechanical assist devices in US patients. Although this may have resulted in some duplication of patients, this was thought to be considerably outweighed by the unique data contributed by each study. Furthermore, two studies included patients as young as 15 years old. However, these studies were still included for analysis as young patients only represented a small proportion of the total sample size.
In one study, LVAD failure was defined as malfunction leading to device exchange or device-related death. In the remaining studies, device failure was defined as malfunction necessitating explantation or replacement.
Demographics and LVAD Types
The baseline demographics are summarized in Table 2. A total of 5,471 patients were included in the present analysis. Of these, 77.7% were male, and the mean weighted age was 54.8 years. Ischemic heart disease was the etiology of cardiac failure in 44.1% of patients. On average, 26.4% of patients were diabetic and 53.3% hypertensive. The CF-LVADs used included the HeartMate II, EVAHEART, Heartware, and Duraheart devices.
Device Failure
The incidence and etiology of device failure is summarized in Table 3. The mean duration of LVAD support was 504.7 days, and the weighted incidence of device failure was relatively low, at 3.9%. For patients with LVAD failure, the average time to device exchange or malfunction was 539.7 days, though this varied greatly (Table 3). The primary etiology of device failure varied considerably amongst the studies, with pump thrombosis being the most common cause overall (50.5% of total device failures). This was followed by lead or cable damage (21.7%), mechanical pump failure (11.6%), device infection (11.1%), and surgical complications associated with the LVAD implantation procedure (2.5%). Other causes of failure reported in one study included unsustained left ventricular recovery following explantation of a pre-existing LVAD (n=1).
Long-term LVAD Durability and Survival
Data were interpolated from the competing outcomes and Kaplan-Meier curves of eight studies to approximate long-term rates of device failure and survival with the original LVAD in place. These outcomes are summarized in Table 4. Analysis using weighted means revealed rates of device failure of 0.5%, 1.8%, 2.9%, 4.5% and 6.5% at 2-, 6-, 12-, 18- and 24-months post implantation, respectively. The weighted survival with the original device in place was 90.2% at 2 months, declining to 54.4% at 12 months, and 38.7% at 24 months.
Publication Bias
Inspection of the funnel plot (Figure 2) did not show significant asymmetry when overall incidence of device failure was selected as an outcome. Egger's linear regression method suggested that publication bias was not a significant influencing factor (P=0.81520). Trim-and-fill analysis revealed that there were no missing studies, and thus no change in overall effect size was observed. These trends suggest that publication bias did not have a significant influence on the presented analysis.
(Enlarge Image)
Figure 2.
Funnel plot for assessment of publication bias in systematic review for durability of continuous-flow left ventricular assist devices. The logit event rate for device failure (horizontal axis) is presented against the standard error (SE) of the log of logit event rate (vertical axis). The SE inversely corresponds to the study size. Asymmetry of the plot may indicate publication bias. Open circles indicate included studies, while any filled circles (none) would represent imputed studies identified through trim-and-fill analysis.
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