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Maximal coronary vasodilator capacity of orthotopic heart transplants in patients with and without rejection
A Nitenberg1, O Tavolaro, D Loisance
1Service de Physiologie et d'Explorations Fonctionnelles, Institut National de la Santé et de la Recherche Médicale Unité 251, Centre Hospitalier Universitaire Xavier-Bichat, Paris, France.
Insights
Heart transplant rejection significantly impairs coronary vascular reactivity, indicating microvascular abnormalities. This suggests the coronary circulation plays a crucial role in the rejection process, impacting blood flow and resistance.
Area of Science:
- Cardiology
- Transplantation Immunology
- Vascular Physiology
Background:
- Cardiac allograft rejection can involve myocardial ischemia.
- Coronary vascular reactivity is critical post-heart transplantation.
Purpose of the Study:
- To assess coronary vascular reactivity in heart transplant recipients.
- To differentiate reactivity in patients with and without rejection.
Main Methods:
- Measured coronary sinus blood flow and resistance before and after dipyridamole infusion.
- Compared 8 non-rejection patients, 5 rejection patients, and 8 controls.
- All patients had normal coronary arteriograms.
Main Results:
- Dipyridamole increased blood flow significantly less in rejection patients (45%) vs. controls (303%) and non-rejection patients (212%).
- Coronary resistance reduction was significantly blunted in rejection patients (36%) vs. controls (77%) and non-rejection patients (73%).
- Coronary flow and resistance reserves were dramatically impaired in rejection patients.
Conclusions:
- Impaired coronary reserve in heart rejection is linked to coronary microvasculature abnormalities.
- The coronary circulation is significantly involved in the cardiac allograft rejection process.
Abstract:
In cardiac allograft rejection, histopathologic changes suggesting that myocardial ischemia is a component of the rejection process have been documented. To further define the coronary vascular reactivity of human heart transplant, coronary sinus blood flow and coronary resistance were measured before and after intravenous dipyridamole within the first year after transplantation in 8 patients without rejection (group II) and in 5 patients with rejection (group III). All had normal coronary arteriograms. Results were compared to those of 8 control subjects (group I). After dipyridamole, coronary sinus blood flow was increased in groups I, II and III by 303, 212 (p less than 0.01 vs group I) and 45%, respectively (p less than 0.001 vs groups I and II). Coronary resistance was reduced by 77, 73 (not significant vs group I) and 36%, respectively (p less than 0.001 vs groups I and II). Concomitantly, coronary sinus blood oxygen content was increased by 172, 145 (not significant vs group I) and 78%, respectively (p less than 0.001 vs group I, not significant vs group II). Thus, the coronary flow reserve evaluated by the dipyridamole/basal coronary sinus blood flow ratio and the coronary resistance reserve evaluated by the basal/dipyridamole coronary resistance ratio were dramatically impaired in group III (1.56 +/- 0.09 and 1.63 +/- 0.30, respectively, p less than 0.001 vs groups I and II). In contrast, they were almost normal in group II (3.11 +/- 0.42 vs 4.03 +/- 0.52 in group I, p less than 0.02, and 3.83 +/- 0.78 vs 4.45 +/- 0.81 in group I, difference not significant). Thus, the impairment of coronary reserve during heart rejection should be linked to abnormalities of the coronary microvaculature. This emphasizes the important involvement of the coronary circulation in the rejection process.