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Left ventricular contractility and contractile reserve in humans after cardiac transplantation
Insights
Transplanted human hearts, though denervated, show normal left ventricular contractility and contractile reserve. This study utilized load-independent measures to assess heart function in transplant recipients compared to healthy controls.
Area of Science:
- Cardiology
- Transplantation Medicine
- Physiology
Background:
- Assessing left ventricular (LV) contractility and reserve in transplanted hearts is challenging due to confounding loading conditions.
- Limited data exist on the functional capacity of chronically denervated, transplanted human hearts.
Purpose of the Study:
- To evaluate LV contractility and contractile reserve in non-rejecting, chronically denervated transplanted hearts.
- To differentiate intrinsic contractility from loading conditions in heart transplant recipients.
Main Methods:
- Echocardiography and calibrated carotid pulse tracings were used to measure load-independent end-systolic indexes.
- Ten heart transplant patients and ten age-matched healthy controls were studied.
- Left ventricular contractility was assessed during methoxamine infusion (afterload challenge); contractile reserve was measured with dobutamine plus methoxamine.
Main Results:
- Baseline LV percent fractional shortening was higher in transplant patients, but this was associated with significantly lower end-systolic wall stress.
- Analysis of LV end-systolic pressure-dimension and stress-shortening relationships revealed no significant differences in contractility between groups.
- No differences in contractile reserve were observed between transplant recipients and control subjects.
Conclusions:
- The chronically denervated, transplanted, non-rejecting human left ventricle exhibits normal intrinsic contractility.
- Transplanted hearts demonstrate preserved contractile reserve comparable to healthy individuals.
- Load-independent assessment is crucial for accurately evaluating cardiac function post-transplant.
Abstract:
Limited data are available concerning left ventricular contractility and contractile reserve in the chronically denervated, transplanted human heart. This is primarily because of the inability of traditional tests of left ventricular performance to distinguish changes in contractility from alterations in ventricular loading conditions. In this study, load-independent end-systolic indexes of left ventricular contractility were measured by echocardiography and calibrated carotid pulse tracings in 10 patients who had undergone orthotopic cardiac transplant (age 48 +/- 4 years; interval from operation to study 1.2 +/- 0.8 years) and in 10 normal control subjects (age 25 +/- 4 years) matched for donor heart age (25 +/- 6 years). None of the transplant patients had evidence of rejection as determined by endomyocardial biopsy. Baseline left ventricular contractility was assessed over a wide range of afterload generated by infusion of methoxamine. Contractile reserve was measured as the response to an infusion of dobutamine plus methoxamine. Before afterload challenge, baseline left ventricular percent fractional shortening was higher for the transplant patients than for the control subjects (36.5 +/- 5.7% vs 32.1 +/- 2.1%; p less than .05). These differences occurred at a time that end-systolic wall stress (a measure of afterload) was significantly lower for the transplant patients (38 +/- 16 vs 50 +/- 9 g/cm2; p less than .05). When the left ventricular end-systolic pressure-dimension and stress-shortening relationships were determined for the transplant and control subjects, no differences in contractility or contractile reserve were noted. Thus the chronically denervated, transplanted, nonrejecting human left ventricle demonstrates normal contractile characteristics and reserve.