The association of rate pressure product (RPP) and myocardial perfusion imaging (MPI) findings: a preliminary study

Introduction: The product of heart rate and systolic blood pressure, termed as rate-pressure product (RPP), is a very reliable indicator of myocardial oxygen demand and is widely used clinically. There have been previous attempts to describe the relationship between RPP and the onset of pain in angina pectoris. The current study aimed to evaluate the association between RPP results and scan findings. Materials and methods: In total, 497 patients with suspected coronary artery disease (CAD) underwent gated, single-photon emission computed tomography (SPECT) imaging with dipyridamole, exercise, or dobutamine stress, and were included in this study. Baseline and maximum heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and electrocardiogram (ECG) results were recorded. The rate-pressure product (RPP) was calculated as the product of heart rate and systolic arterial pressure for both baseline and maximum measures. The difference between the RPP max and the basal RPP is known as the RPP reserve. Researchers also obtained semi-quantitative analyses of myocardial perfusion imaging (MPI), using gated software, demographic information, risk factors of CAD, and pretest likelihoods of CAD using nomograms. Result: Four hundred and ninety-seven cases, including 426 patients with dipyridamole stress, 59 with exercise stress, and 12 with dobutamine stress, underwent myocardial perfusion imaging. Scan results were positive in 194 (45.5%) and negative in 232 (54.5%) patients with dipyridamole stress. In patients with exercise stress, the scan was positive in 24 (40.7%) cases and negative in 35 (59.3%) cases. In dobutamine stressed patients, the scan was positive in 6 (50%) cases and negative in the 6 remaining cases. Dipyridamole stress resulted in a significant difference between HR at rest and at maximum (28.95 +/- 24.53, p-value < 0.0001), between systolic BP at rest and maximum (6.75 +/- 12.50, p-value < 0.0001) and between diastolic BP at rest and maximum (1.45 +/- 5.80; p-value < 0.0001). There was a significant correlation between sum stress scores (SSS) and reserved RPP (r=-0.12, p-value < 0.001) which, in dipyridamole patients, was r=-0.18, p-value=0.0001). In addition, there was a significant association between reserved RPP and risk of CAD (p-value < 0.001). In the patients with dipyridamole stress, the ejection fraction (EF) change (odds ratio =0.92; 95% CI: 0.86-0.98; p=0.01), reserve RPP (odds ratio =1.00; 95% CI: 1.00-1.00; p=0.04), risk of CAD (odds ratio =5.80; 95% CI: 3.21-10.50; p < 0.0001) and age (odds ratio =0.94; 95% CI: 0.89-0.98; p=0.01) were associated significantly with MPI results, using multiple logistic regressions. Conclusion. The study demonstrated that RPP is associated with MPI findings using gated SPECT imaging with dipyridamole stress. However, to confirm this preliminary result, further studies are mandatory.