Key result
During dobutamine stress echocardiography, an increase in heart rate of at least 50 bpm from baseline resulted in a normal coronary flow reserve (≥2) in 97.2% of patients.
Observational (n=33)
No
Effect estimate: r=0.84 (95% CI 93-99.2)
p-value: p=<0.001
During dobutamine stress echocardiography, achieving a heart rate increase of 50 bpm from baseline or 75% of the maximum predicted heart rate is sufficient to adequately evaluate coronary flow reserve in the left anterior descending artery.
A 50 bpm HR rise may suffice for CFR assessment in DSE; this Level 3 finding leaves open prospective validation before practice change.
BACKGROUND: The determination of coronary flow reserve (CFR) is an essential concept at the moment of decision-making in ischemic heart disease. There are several direct and indirect tests to evaluate this parameter. In this sense, dobutamine stress echocardiography is one of the pharmacological method most commonly used worldwide. It has been previously demonstrated that CFR can be determined by this technique. Despite our wide experience with dobutamine stress echocardiography, we ignored the necessary heart rate to consider sufficient the test for the analysis of CFR. For this reason, our main goal was to determine the velocity of coronary flow in each stage of dobutamine stress echocardiography and the heart rate value necessary to double the baseline values of coronary flow velocity in the territory of the left anterior descending (LAD) coronary artery. METHODS: A total of 33 consecutive patients were analyzed. The patients included had low risk for coronary artery disease. All the participants underwent dobutamine stress echocardiography and coronary artery flow velocity was evaluated in the distal segment of LAD coronary artery using transthoracic color-Doppler echocardiography. RESULTS: The feasibility of determining CFR in the territory of the LAD during dobutamine stress echocardiography was high: 31/33 patients (94%). Mean CFR was 2.67 at de end of dobutamine test.There was an excellent concordance between delta HR (difference between baseline HR and maximum HR) and the increase in the CFR (correlation coefficient 0.84). In this sense, we found that when HR increased by 50 beats, CFR was ≥ 2 (CI 93-99.2%). In addition, 96.4% of patients reached a CFR ≥ 2 (IC 91.1 - 99%) at 75% of their predicted maximum heart rate. CONCLUSIONS: We found that the feasibility of dobutamine stress echocardiography to determine CFR in the territory of the LAD coronary artery was high. In this study, it was necessary to achieve a difference of 50 bpm from baseline HR or at least 75% of the maximum predicted heart rate to consider sufficient the test for the analysis of CFR.
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Forte et al. (2011) conducted an observational in Low risk for coronary artery disease (n=33). Dobutamine stress echocardiography vs. Baseline was evaluated on Proportion of patients achieving coronary flow reserve ≥ 2 when heart rate increased by ≥ 50 bpm (r=0.84, 95% CI 93-99.2, p=<0.001). During dobutamine stress echocardiography, an increase in heart rate of at least 50 bpm from baseline resulted in a normal coronary flow reserve (≥2) in 97.2% of patients.
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