Recovery mismatch between myocardial blood flow and cardiac workload after physical exercise: a positron emission tomography study.
AIMS
We studied the interrelation between oxygen consumption and myocardial blood flow (MBF) during recovery. MBF is directly dependent on oxygen consumption. The latter is linearly related to the heart rate-blood pressure product (RPP, bpm × mmHg), an index reflecting external cardiac work. In the immediate post-exercise period, cardiac output decreases considerably. This is expected to be paralleled by a rapid fall in oxygen demand, rendering ischaemia unlikely. Thus, the phenomenon of ST-segment depression during recovery remains unexplained.


METHODS AND RESULTS
(15)O-labelled water and positron emission tomography were used to measure MBF in 14 young healthy volunteers (mean age 27 ± 3 years) during the following study conditions: (i) at rest, (ii) during a steady submaximal supine bicycle exercise stress within the scanner, and (iii) during recovery immediately after cessation of exercise. During recovery, RPP decreased by 43% (18 768 ± 1337 vs. 11 652 ± 3224, P < 0.001). In contrast, the associated decrease in MBF (2.52 ± 0.52 vs. 1.93 ± 0.50 mL/min/g, P < 0.001) and perfusion reserve (2.68 ± 0.51 vs. 2.03 ± 0.42, P < 0.001) was significantly less pronounced (-24%, P < 0.01), indicating a relative delay in MBF recovery compared with cardiac work load.


CONCLUSION
The mismatch between a rapid decrease in cardiac workload but preserved hyperaemic response early after cessation of physical exercise suggests an uncoupling of cardiac work and MBF during recovery.
['Siegrist|Patrick T|PT|', 'Koepfli|Pascal|P|', 'Namdar|Mehdi|M|', 'Pazhenkottil|Aju P|AP|', 'Nkoulou|Rene|R|', 'Lüscher|Thomas F|TF|', 'Kaufmann|Philipp A|PA|']
D000328:Adult D002302:Cardiac Output D003326:Coronary Circulation D005080:Exercise Test D005260:Female D005500:Follow-Up Studies D064368:Healthy Volunteers D006321:Heart D006339:Heart Rate D006801:Humans D008297:Male D009206:Myocardium D010101:Oxygen Consumption D049268:Positron-Emission Tomography D011237:Predictive Value of Tests D020127:Recovery of Function D012016:Reference Values D012146:Rest D012680:Sensitivity and Specificity
Recovery Myocardial blood flow Physical exercise PET