Imaging the Physiology of the Ischemic Cascade

Abstract

Stress cine function and vasodilating stress perfusion are commonly used approaches for the evaluation of ischemic heart disease. Both imaging approaches, using either stress echocardiography or stress nuclear scintigraphy, have stood the test of time as highly accurate in diagnosing coronary artery stenosis and as prognostic tools in patients with symptoms suspicious of myocardial ischemia.1,2 When epicardial coronary flow is interrupted and leads to an imbalance between myocardial oxygen supply and demand, reduced myocardial perfusion, regional ventricular dysfunction, and ECG change occur in quick succession; hence, the term “ischemic cascade” has been described.3 This phenomenon has been well described after acute balloon inflation during percutaneous coronary intervention and also during demand ischemia induced by dobutamine stress. Consequently, capturing abnormalities of both perfusion and function, in an attempt to improve the diagnostic performance of noninvasive tests, has been the focus of investigation using echocardiography and nuclear scintigraphy, with encouraging results.4–6 Article p 122 In this issue of Circulation: Cardiovascular Imaging , Gebker et al7 described the diagnostic utility of cardiac MRI (CMR) for evaluation of coronary artery disease using both myocardial perfusion (DSMRP) and function (DSMR) assessments during high-dose dobutamine stress testing. As shown in their work, CMR has technical features that are well suited for imaging both perfusion and regional function during a single, high-dose dobutamine infusion. With advances in imaging speed and algorithms of accelerated data reconstruction, gated cine steady-state free precession imaging can capture regional left ventricular dysfunction from ischemia at high temporal resolution and contrast-to-noise ratio. At target heart rates during peak stress, first-pass perfusion can sample myocardial …