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Understanding blood pressure and vascular haemodynamics in implanted Left Ventricular Assist Device patients.

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New Insight into the consequences of implanting artificial heart pumps

An increasing number of heart failure (HF) patients depend on continuous-flow left ventricular assist devices (LVADs) for survival. To understand the risks associated with LVADs, scientists have investigated the unique blood flow and pressure profiles of HF patients implanted with LVADs.

Health

Heart transplant is the preferred and most successful therapy for patients with advanced HF but a shortage of available donor hearts poses a significant limitation to this life-saving intervention. Since the introduction of LVADs, survival rates of HF patients have significantly improved. However, these patients are at high risk of stroke and gastrointestinal bleeding, most probably because of the low pulsatile flow and pressure output from the LVAD.

Continuous measurement of blood pressure and flow in LVAD patients

It is debatable whether humans need a pulsatile circulation for optimal health. Therefore, it is critical to understand how the unique LVAD specific blood pressure and flow patterns, known as haemodynamics, interact across the entire circulation. With the support of the Marie Skłodowska-Curie programme, scientists of the HIT-LVAD project have worked to address this issue by collecting macro and micro-vascular blood flow data in patients implanted with LVADs. A collaborative study with Columbia University’s Irving Medical Center (CUIMC), which is the number one medical centre in the world and has one of the largest LVAD programmes, enabled the Marie Skłodowska-Curie research fellow Eric Stöhr of Cardiff Metropolitan University to attend CUIMC to recruit and measure blood flow and blood pressure in the largest cohort of LVAD patients to date. “The goal was to understand the physiological consequences of having an LVAD and to transfer this knowledge and expertise back to Europe where many of these patients also receive this therapy″ he explains. The HIT-LVAD project has generated the world’s largest database of blood flow and blood pressure in LVAD patients. It developed and validated a new device capable of measuring blood pressure (BP) over 24 hours in LVAD patients. This advancement may help clinicians improve diagnostic accuracy of BP measurement even at night and has allowed for a more accurate comparison with the blood pressure of healthy individuals. Additionally, the HIT-LVAD project revealed that LVAD patients have different blood flow in small arteries compared with other humans, challenging the current perception in the field regarding macro and microvascular blood flow dynamics. Thus, the project provides a more holistic view of blood flow and BP in LVAD patients, with important consequences for medical management.

HIT-LVAD impact and future prospects

“The HIT-LVAD trial has provided the field of medicine with a physiological understanding of the flow and pressure profiles that LVADs actually transmit into the microcirculation, which could potentially explain the microvascular damage seen in these patients,″ emphasises trial supervisor Barry McDonnell. These findings will improve the clinicians' understanding of their patients' overall health status, enabling the development of improved LVAD therapy and BP monitoring in this patient group. Development of a new state of the art BP monitor specifically for LVAD patients, is currently underway by the HIT-LVAD team. Future plans include follow-up and outcome monitoring of LVAD patients already assessed, to understand and better predict risk in the future. With an ever-increasing aged population, current estimations predict that HF may become the most prevalent disease world-wide. With a view to the future, Stöhr is confident that “the HIT-LVAD project provides important new insight that will improve the understanding, monitoring and treatment of current and future LVAD patients.″

Keywords

HIT-LVAD, ventricular assist devices (LVADs), heart failure (HF), blood pressure, haemodynamics

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