102. Nuclear and Multimodality Imaging: Myocardial Viability

CardioNerd Amit Goyal is joined by Dr. Erika Hutt (Cleveland Clinic general cardiology fellow), Dr. Aldo Schenone (Brigham and Women’s advanced cardiovascular imaging fellow), and Dr. Wael Jaber (Cleveland Clinic cardiovascular imaging staff and co-founder of Cardiac Imaging Agora) to discuss nuclear and complimentary multimodality cardiovascular imaging for the evaluation of myocardial viability. Show notes & #Tweetorial were created by Dr. Hussain Khalid (University of Florida general cardiology fellow and CardioNerds Academy fellow in House Thomas). To learn more about multimodality cardiovascular imaging, check out Cardiac Imaging Agora! 

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Show Notes & Take Home Pearls

In response to ischemia the myocardium can dynamically change along a spectrum from myocardial stunning to myocardial hibernation to myocardial necrosis. The goals of viability testing are to identify patients who may benefit from revascularization as hibernating or stunned myocardium are potentially reversible causes of LV dysfunction. There are numerous imaging modalities available for the evaluation of myocardial viability. The broad range of ways in which myocardial viability is assessed speaks to the complexity of the disease spectrum and the difficulty in creating a unifying definition of viability to assess in clinical trials.  

Five Take Home Pearls

1. In response to an acute episode of ischemia with subsequent reperfusion, the myocardium can be exposed to a large flux of oxygen free radicals or calcium overload that affects the cellular membrane and contractile apparatus. This phenotypically results in decreased contractility of the affected region of myocardium that can persist for weeks, labeled myocardial stunning 

2. Repeated episodes of myocardial stunning or chronic low myocardial blood flow can lead to cellular changes such as resorption of the contractile apparatus in order to decrease oxygen demand and allow the myocardial cells to survive. Phenotypically, this might appear as regions of hypokinesis or akinesis at rest with a fixed perfusion defect on myocardial perfusion imaging. This is typically considered hibernating myocardium.  

3. The goal of myocardial viability testing is to be able to differentiate between stunned, hibernating and necrosed myocardium. In patients with known epicardial coronary disease, this differentiation allows us to identify who may benefit from revascularization with improved LV systolic function and overall survival.  

4. There are several imaging modalities that can be used in the assessment of myocardial viability. The most sensitive modalities are FDG-PET and CMR. The addition of Dobutamine or first pass perfusion with Gadolinium additionally increases the specificity of CMR. These modalities are more expensive and not as widely available.  

5. The dynamic nature of the myocardial hibernation and the lack of a unifying definition/phenotypic expression of myocardial hibernation and viability have made it difficult for clinical trials to show that re-establishing myocardial blood flow to hibernating myocardium is beneficial. As Dr. Jaber stated in the episode in his spin on the classic opening phrase from Leo Tolstoy’s masterpiece, Anna Karenina, “All normal hearts are normal in the same way, and all abnormal hearts are abnormal in different ways.” 

6. The PARR-2 trial was one of the few randomized, controlled trials of patients with LV systolic dysfunction and coronary artery disease who were randomized to either FDG-PET guided management or standard care with respect to whether to pursue revascularization. Overall,