Related Experiment Video
Updated: Jun 23, 2026
Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats
Published on: June 28, 2019
Coronary vasodilator reserve in primary and secondary left ventricular hypertrophy. A study with positron emission
L Choudhury1, S D Rosen, D Patel
1Cyclotron Unit, Hammersmith Hospital, London, U.K.
Insights
Coronary vasodilator reserve is reduced in hypertrophic cardiomyopathy and secondary left ventricular hypertrophy. The impairment is more pronounced in hypertrophic cardiomyopathy patients, despite similar baseline myocardial blood flow.
Area of Science:
- Cardiology
- Physiology
Background:
- Coronary vasodilator reserve is diminished in hypertrophic cardiomyopathy (HCM) and secondary left ventricular hypertrophy (LVH) with normal coronary arteries.
- Quantitative differences in this impairment between HCM and secondary LVH are not well-established.
Purpose of the Study:
- To quantitatively compare coronary vasodilator reserve between patients with HCM and secondary LVH.
- To assess the extent of impairment in coronary vasodilator reserve in these conditions.
Main Methods:
- Positron emission tomography with H2(15)O was used to measure myocardial blood flow at rest and during dipyridamole stress.
- Myocardial blood flow was assessed in 12 HCM patients, 16 secondary LVH patients, and age- and sex-matched controls.
- Coronary vasodilator reserve was calculated as the ratio of hyperemic to baseline myocardial blood flow.
Main Results:
- Baseline myocardial blood flow did not differ significantly between patient groups and their respective controls.
- Post-dipyridamole myocardial blood flow was significantly lower in HCM patients compared to controls (P=0.0001).
- Coronary vasodilator reserve was significantly reduced in both HCM (2.05 vs 3.81, P=0.0001) and secondary LVH (2.06 vs 2.90, P<0.03) patients compared to controls, with a greater reduction in HCM.
Conclusions:
- Both HCM and secondary LVH exhibit impaired coronary vasodilator reserve, even after adjusting for cardiac workload.
- The reduction in coronary vasodilator reserve is quantitatively greater in HCM patients than in secondary LVH patients.
- In secondary LVH, a higher baseline myocardial blood flow partially offsets the blunted hyperemic response, contributing to a less severe reduction in overall vasodilator reserve compared to HCM.
Objectives:
Coronary vasodilator reserve is reduced in hypertrophic cardiomyopathy and secondary left ventricular hypertrophy despite angiographically normal coronaries. The aim of the present study was to assess whether quantitative differences exist between these conditions.
Methods:
Using positron emission tomography with H2(15)O, myocardial blood flow was measured at baseline and following intravenous dipyridamole (0.56 mg.kg-1) in 12 hypertrophic cardiomyopathy patients (age 34 (11) years, mean (SD), all male), 16 secondary left ventricular hypertrophy patients (age 58 (20) years, P < 0.01 vs hypertrophic cardiomyopathy; 10 female) and 40 normal controls (age 54 (20), 13 female). In view of the known decline of post-dipyridamole myocardial blood flow with age, myocardial blood flow was compared between the patient groups and appropriately matched subsets of the total control group.
Results:
Baseline myocardial blood flow in the hypertrophic cardiomyopathy patients was 0.82 (0.23) ml.min-1.g-1 vs 0.94 (0.14) ml.min-1.g-1 in its matched control group, P = ns. For the secondary left ventricular hypertrophy patient group, baseline myocardial blood flow was 1.17 (0.40) ml.min-1.g-1 vs 1.06 (0.28) ml.min-1.g-1 for the secondary left ventricular hypertrophy matched control group, P = ns. Following dipyridamole, myocardial blood flow was 1.64 (0.44) ml.min-1.g.-1 in hypertrophic cardiomyopathy patients vs 3.50 (0.95) ml.min-1.g-1 for the hypertrophic cardiomyopathy matched control group, P = 0.0001. For the left ventricular hypertrophy patients, post-dipyridamole myocardial blood flow was 2.27 (0.60) ml.min-1.g-1 vs 2.94 (1.29) ml.min-1.g-1 for the left ventricular hypertrophy controls, P = 0.06. Coronary vasodilator reserve (dipyridamole-myocardial blood flow/baseline-myocardial blood flow) was 2.05 (0.61) for hypertrophic cardiomyopathy patients vs 3.81 (0.98) for the hypertrophic cardiomyopathy controls (P = 0.0001, patients vs controls) and 2.06 (0.62) for left ventricular hypertrophy patients vs 2.90 (1.38) for the left ventricular hypertrophy controls, P < 0.03 patients vs controls. After correction of baseline myocardial blood flow for baseline heart rate x systolic pressure product, coronary vasodilator reserve for the hypertrophic cardiomyopathy patients was 2.06 (1.06) vs 4.34 (1.54) for the hypertrophic cardiomyopathy controls. P = 0.0002 and in the secondary left ventricular hypertrophy patients, the values were 2.13 (0.64) vs 2.89 (1.42) in the secondary left ventricular hypertrophy controls, P < 0.05.
Conclusion:
In both hypertrophic cardiomyopathy and secondary left ventricular hypertrophy, the computed coronary vasodilator reserve is impaired, even after correction for baseline cardiac work. However, the extent of the reduction is greater in the hypertrophic cardiomyopathy patients. In the blunting of vasodilator reserve of secondary left ventricular hypertrophy, the patients' greater hyperaemic response is partly offset by the higher baseline myocardial blood flow.
