EXERCISE RESPONSE AFTER CARDIAC TRANSPLANTATION - CORRELATION WITH SYMPATHETIC REINNERVATION

Objective-To investigate the relation between sympathetic efferent rei nnervation and chronotropic competence during exercise testing after c ardiac transplantation. Patients-Twenty five long-term cardiac transpl ant recipients and 11 normal controls. Setting-Regional cardiothoracic centre. Methods-Intracoronary tyramine was given to the transplant re cipients and the per cent heart rate change measured. Exercise tests w ere performed in patients and controls according to the chronotropic a ssessment exercise protocol, and the per cent heart rate reserve measu red at peak exercise and 6 min afterwards to estimate the recovery rat e. Results-The mean (SD) percentage heart rate change after intracoron ary tyramine was 15.7 (15.4). Heart rate reserve achieved at peak exer cise was 68.3 (20.6)% compared with 102.7 (9.3)% in the controls (P < 0.001). Heart rate recovery at 6 min was 41.7 (20.1)% compared with 79 .5 (9.0)% in the controls (P < 0.001). Total workload was 69.0 (33.0) METS.min compared with 117.2 (41.9) METS.min in the controls (P < 0.01 ). There was a positive correlation between heart rate reserve achieve d at peak exercise and response to tyramine (r = 0.66, P < 0.01), betw een heart rate recovery and response to tyramine (r = 0.69, P < 0.001) , and between total workload and response to tyramine (r = 0.63, P = 0 .04).Conclusion-Functional sympathetic efferent reinnervation of the s inus node occurred in some patients after transplantation, and was ass ociated with improved heart rate response during and recovery after ex ercise, as well as with increased total workload.