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Editor,—The recent study by Fraundet al has highlighted the improving survival of cardiac transplant recipients with a 10 year survival rate of approaching 50%.1 Functional status in long term survivors was encouraging with fewer than one in five patients experiencing (New York Heart Association) NYHA class III or IV symptoms. These findings reinforce cardiac transplantation as a valuable treatment option for patients with symptomatic severe left ventricular systolic dysfunction.
Disappointingly, the authors were unable to identify any useful factors that potentially could be used to predict long term outcome. Allograft vasculopathy is now emerging as the main factor limiting long term survival, and 39% of all deaths in the study were attributable to this complication. Angiographic screening programmes for the detection of allograft vasculopathy have been instituted but, without the routine use of intravascular ultrasound techniques, coronary angiography has been shown systematically to underestimate this form of coronary disease. Furthermore, as no adequate therapeutic options currently exist, the value of screening that exposes many stable patients to the risk of an expensive invasive procedure has been questioned.2 Clearly, a non-invasive method of identifying high risk patients would be highly desirable.
Echocardiography plays an important role in the follow up of recipients after cardiac transplantation but, other than assessment of left ventricular systolic function by ejection fraction, it did not feature in Fraund et al's article. In the past efforts have focused specifically on the use of Doppler studies in detecting acute allograft rejection. Its clinical utility is now expanding. Recently, dobutamine stress echocardiography has been scrutinised for the detection of allograft vasculopathy. This method of assessment focuses on the functional significance of ischaemia rather than the specific coronary anatomy; therefore, it has introduced a new approach to the evaluation of recipients. Importantly, stress echocardiography has been shown to have a high negative predictive value for determining future cardiac events and death.3 A major advantage is that it is non-invasive, but reservations exist regarding the potential for high interobserver variability, which could jeopardise the value of the information derived.
The importance of abnormalities of left ventricular diastolic function is now being appreciated. The presence of a restrictive pattern of left ventricular filling independently predicts an adverse outcome in patients with a range of conditions including acute myocardial infarction. In cardiac allografts, diastolic dysfunction has a multifactorial cause. Valentine et al have shown that recovery of diastolic function after allograft rejection may often be incomplete, with the development of restrictive physiology in a proportion of recipients characterised by an increase of left ventricular end diastolic pressure.4 The histological appearance in these circumstances is one of myocyte loss and fibrous replacement. An irreversible decline in compliance may develop leading to chronically deranged diastolic function while systolic function may be preserved by hypertrophy of intact myocytes.
Cumulative myocardial damage leading to chronic diastolic dysfunction has important implications for the long term prognosis of heart transplant recipients.5 ,6 Those with restrictive physiology are significantly more likely to experience NYHA class III or IV symptoms.4 Ross et alhave shown that preservation of normal Doppler parameters of diastolic function in the early post-transplantation period confers a significant actuarial survival advantage, which is independent of the influence of other factors such as allograft vasculopathy.5
In experienced hands both resting Doppler and dobutamine stress echocardiography allow the non-invasive identification of heart transplant recipients at high risk of an adverse outcome. Whether this group will benefit from more aggressive treatment and careful follow up remains to be determined.