The ever-changing field of mechanical circulatory support: new challenges at the advent of the 'single device era'

Extracorporeal driveline vibrations to detect left ventricular assist device thrombosis - A porcine model study

BACKGROUND

Pump thrombosis (PT) and related adverse complications contributed to the HeartWare Ventricular Assist Device (HVAD) market withdrawal. Many patients still receive lifelong support, with deficient PT surveillance based on pump power trends. Analysis of pump vibrations is better for detecting PT. Here, we investigated the feasibility of an extracorporeal accelerometer to detect PT from pump vibrations propagated out on the driveline.

METHODS

In a porcine HVAD model (n = 6), an accelerometer was attached to the pump as a reference and another to the driveline for comparisons of signals. In total, 59 thrombi were injected into the heart to induce PT, followed by intermittent thrombus washout maneuvers. Signals were compared visually in spectrograms and quantitatively in third harmonic saliences (S3H) by correlation analysis. Receiver operating characteristic curves expressed the method's outcome in sensitivity vs specificity, with the overall diagnostic performance in the area under the curve (AUC) score.

RESULTS

Five experiments had good driveline signal strength, with clear spectrographic relationships between the 2 accelerometers. Third harmonic driveline vibrations were visible 20 vs 30 times in the reference. The comparison in S3H showed a strong correlation and yielded an AUC of 0.85. Notably, S3H proved robust regarding noise and false PT detections.

CONCLUSIONS

An extracorporeal accelerometer on the driveline can be a readily available method for accurate HVAD PT detection before an accelerometer integration with left ventricular assist device is feasible.

Detection of inflow obstruction in left ventricular assist devices by accelerometer: A porcine model study

BACKGROUND

Left ventricular assist devices (LVAD) provide circulatory blood pump support for severe heart failure patients. Pump inflow obstructions may lead to stroke and pump malfunction. We aimed to verify in vivo that gradual inflow obstructions, representing prepump thrombosis, are detectable by a pump-attached accelerometer, where the routine use of pump power (PLVAD) is deficient.

METHOD

In a porcine model (n = 8), balloon-tipped catheters obstructed HVAD inflow conduits by 34% to 94% in 5 levels. Afterload increases and speed alterations were conducted as controls. We computed nonharmonic amplitudes (NHA) of pump vibrations captured by the accelerometer for the analysis. Changes in NHA and PLVAD were tested by a pairwise nonparametric statistical test. Detection sensitivities and specificities were investigated by receiver operating characteristics with areas under the curves (AUC).

RESULTS

NHA remained marginally affected during control interventions, unlike PLVAD. NHA elevated during obstructions within 52-83%, while mass pendulation was most pronounced. Meanwhile, PLVAD changed far less. Increased pump speeds tended to amplify the NHA elevations. The corresponding AUC was 0.85-1.00 for NHA and 0.35-0.73 for PLVAD.

CONCLUSION

Elevated NHA provides a reliable indication of subclinical gradual inflow obstructions. The accelerometer can potentially supplement PLVAD for earlier warnings and localization of pump.

Ventricular Assist Devices: Challenges of the One-device Era

Heart failure (HF) is linked to to high mortality rates and recurrent hospitalisations despite medical and device-based achievements. The use of left ventricular assist devices (LVADs) has improved survival among patients with advanced HF. Significant progress has been achieved with the new generation of continuous-flow devices, particularly with the fully magnetically levitated HeartMate 3. In June 2021, Medtronic announced the abrupt withdrawal of the HeartWare device from the market. This decision has introduced a new era in which the field of mechanical support for advanced HF patients is dominated by a single device - the HeartMate 3. The direct clinical and economic consequences of this change will necessitate new surgical considerations. Because of the expected need for HeartWare device replacement in small patients, new surgical techniques and device adaptation will be needed. The new single-device era will hopefully encourage scientists and engineers to create innovations in the advanced HF arena. Special considerations should be taken during the COVID-19 pandemic when treating patients with LVADs.

Systemic thrombolysis in the management of pump thrombosis in patients with left ventricular assist devices

Left ventricular assist device (LVAD) implantation as destination therapy (DT) is a valuable treatment option in patients with end-stage heart failure ineligible for heart transplant. However, this therapy can be complicated by life-threatening pump thrombosis (PT). This case series reports our single-center experience with a structured systemic thrombolysis protocol in case of PT. Consecutive patients undergoing DT LVAD (HVAD, Medtronic, Framingham, MA) implantation between 2010 and April 2021 at our institution were reviewed and those with PT identified. Clinical, laboratory and LVAD specific data were collected and analyzed retrospectively. All patients with PT were treated with systemic thrombolysis according to a structured bedside protocol. Treatment was defined successful if a patient was alive at 30 days follow-up and free of recurrent PT, stroke or device exchange. Fourteen out of 94 patients experienced a PT after LVAD implantation (11%). Systemic thrombolysis was successful in 10 of 14 patients (71%) at 30 days. Two patients died within 30 days due to a hemothorax and multi-organ failure. In three patients treatment was complicated by a major bleeding; twice a hemothorax (one fatal) and one right calf bleeding. No intracerebral hemorrhage was observed. Three patients experienced a thrombotic complication within 30 days; all recurrent PT. Eleven of the 14 DT patients were discharged home after a limited hospital stay after thrombolysis (average of 11 days). In conclusion, systemic thrombolysis may be a reasonable option for life-threatening PT in this vulnerable DT group in whom device exchange is often impossible due to comorbidity.