An international study has identified the diastolic-systolic velocity ratio (DSVR) as potentially useful in assessing functional stenoses in coronary arteries. The technique, which can be performed either invasively via angiography or noninvasively by echocardiography, could be a useful adjunct to clinical practice, according to Guus de Waard, MD, a cardiology research fellow at VU University Medical Center in Amsterdam, the Netherlands.
de Waard presented the findings from the study during the Melvin Judkins Young Investigator Award Competition on Sunday at Scientific Sessions.
“We found a reasonable diagnostic accuracy for DSVR when we compared it to invasive measurements, such as fractional flow reserve (FFR) to determine whether a stenosis is functionally significant,” de Waard said. “Coronary angiography with FFR remains the gold standard for assessing the functional importance of stenosis, but DSVR could be a useful adjunct in certain scenarios.”
Researchers at four cardiology centers in Great Britain, Spain and the Netherlands collaborated on the project, which compared the diagnostic accuracy of DSVR and FFR, and explored the physiologic mechanisms that underlie DSVR.
Researchers obtained simultaneous measurements of intracoronary pressure and Doppler flow velocity using coronary angiography in 228 stable patients. Measurements also were analyzed after percutaneous intervention in 39 patients.
de Waard reported that DSVR declines with worsening of the FFR, classified into 0.05 unit groups (Ptrend<0.001), and that DSVR shows acceptable diagnostic agreement with FFR at an ischemic threshold of 0.75 and a hyperemic stenosis resistance index threshold of 0.80 mmHg·cm-1·s. The optimal cutoff value for DSVR is 1.74. Because DSVR has a close inverse correlation with the diastolic-systolic resistance ratio (r2=0.83, p<0.001), de Waard said the distribution of vascular resistance among diastole and systole could be interrogated.
The difference between systolic and diastolic stenosis resistance as a percentage of total vascular resistance gradually increases as FFR class worsens (Ptrend<0.001). After PCI, DSVR increased from a mean of 1.56 to 1.77 (p<0.01).
“The most important finding is that we were able to unravel how the DSVR index works,” de Waard said. “Because microvascular resistance is lower during diastole than during systole, while stenosis resistance does not differ for both phases of the cardiac cycle, a stenosis that is functionally significant has a higher impact on diastole than on systole. This results in a decrease of DSVR, which can be measured immediately using ultrasonographic echocardiography.”
However, de Waard noted, DSVR should not be viewed as a replacement for coronary angiography or FFR because ultrasound cannot provide pressure data and is less precise than direct angiographic measurement. He said there are several situations, though, in which a quick, reasonably accurate substitute may be useful.
The most common scenario is the patient who presents in the emergency room with chest pain. Electrocardiography may be inconclusive and a troponin assay may not be immediately available.
Another potentially useful application, he said, might be in noninvasive follow-up for patients after CABG or PCI to monitor graft patency and in-stent restenosis.
“I am not recommending that the DSVR index replace any of the clinical tools we already have in place,” de Waard said. “It should be viewed as an interesting and potentially useful tool to add to our current armamentarium.”