Long-term biventricular support with rotary blood pumps: prospects and pitfalls

Abstract

Congestive heart failure affects 23 million people worldwide, including 7.5 million in North America (670 000 new cases per year) and 7 million in Europe [1]. Since 10% of those over 65 suffer from systolic left ventricular dysfunction, the number of patients with heart failure will double over the next 25 years. At any time, 10% of the heart failure cohort are categorized Stage D with advanced structural heart disease and symptoms at rest, despite detailed medical and cardiac resynchronization therapy. Twenty percent of these are younger than 65 years of age (around 140 000 in both the USA and Europe). The prognosis of Stage D heart failure is grim. In the REMATCH study, only 8% of the medically treated patients were alive at 2 years and continued to suffer in the interim [2]. A recurrent sentiment expressed by the Stage D patients is that they would sacrifice some duration of survival for a period of symptomatic relief [3]. Cardiac transplantation provides this for a highly selected tiny minority [4]. In contrast, cardiac resynchronization therapy is disappointing. A meta-analysis of 14 trials that randomized resynchronization against medical treatment showed only 59% of the NYHA IV device patients to have borderline symptomatic improvement to NYHA III with no survival benefit [5]. Boyle et al. [6] compared functional outcomes for NYHA IV patients after resynchronization or implantation of a left ventricular assist device (LVAD). At 6 months, resynchronized patients achieved only an additional 6 m in the 6 min walk test (insufficient to affect their daily living) and remained NYHA III or IV. In contrast, LVAD patients improved by 341 m, achieving NYHA I or II status. The study could not be randomized because 90% of the LVAD candidates were bed-bound on intravenous inotropes and could not walk beforehand. Long-term mechanical circulatory support is an increasingly realistic ‘off the shelf’ alternative to cardiac transplantation and an effective solution for those rendered ineligible through common heart failure comorbidities [7–9]. The treatment aims are uncontroversial. The first is to provide symptomatic relief and the second to achieve at least 5-year survival with a good quality of life. The third aim is cost containment by reducing the number of hospital admissions to palliate intolerable levels of breathlessness and fatigue. Hospital events account for $20.9 billion of an overall $35 billion heart failure budget in the USA. The rationale for a blood pump deployment is clear. The failing heart beats more than 120 000 times per day pumping around 7000 l of blood against an increasing afterload. As the heart dilates, the ventricular wall tension, myocardial energy and oxygen consumption increase, while sub-endocardial blood flow decreases. The LVAD unloads the failing ventricle resulting in beneficial structural and functional changes in the diseased myocardium [10–12]. Systemic blood flow returns to physiological levels to preserve the coronary and vital organ perfusion [13]. When native heart contractility and segmental wall motion improve, there is less propensity for intraventricular thrombus formation and thromboembolism. In September 2011, the Society of Thoracic Surgeons and the Food and Drugs Administration (USA) assembled a ‘Think Tank’ to focus on the need for long-term mechanical circulatory support in the USA. The group acknowledged the increasing safety profile and reliability of contemporary implantable rotary blood pumps together with the potential for stem cells to broaden the horizons of heart failure management. A need for 40 000 long-term LVADs per year was predicted, which would account for 50% of the heart failure annual budget. Between 15 and 30% of patients require biventricular support and there is no satisfactory long-term mechanical solution for these patients. The pulsatile total artificial hearts have numerous restrictions which confine their use as a bridge to transplantation [14]. INTERMACS data indicate that all total artificial heart patients are transplanted or dead within 6 months [15].