Dilated Cardiomyopathy and Myocardial Infarction
Cardiac magnetic resonance (CMR) is the current golden standard for accurate assessment of ventricular volumes and global and regional function, thus providing information on prognosis.
- •Extracellular accumulation of gadolinium, imaged at 10 to 30 minutes after injection, identifies areas of myocardial fibrosis commonly seen in cardiomyopathies, generally subendocardial or transmural in a coronary distribution in the case of ischemic cardiomyopathy.
- •Transmural extent of LGE can predict recovery of myocardial function after revascularization in patients with coronary artery disease.
- •Negative stress CMR with either adenosine or dobutamine stressors has excellent negative predictive value for subsequent coronary events.
- •Noncoronary segmental distribution and midwall or epicardial involvement of LGE are atypical of myocardial infarction. This allows discrimination between ischemic and nonischemic etiologies of cardiomyopathy, which can assist in clinical decision making.
- •Takotsubo cardiomyopathy is characterized by left ventricular apical dilation and regional hypocontraction, absence of first-pass perfusion abnormality, and minimal or absent concomitant subendocardial LGE.
- •Because of its higher spatial and temporal resolution, CMR can offer an improved assessment for the presence and extend of ventricular noncompaction, compared with echocardiography.
- •CMR can accurately quantify severity of valvular regurgitation and stenosis using phase contrast imaging. In the same study CMR can assess the physiologic impact of the valvular heart disease by providing quantitation of large vessel morphology and ventricular volumes and functions.
- •CMR is the most sensitive technique for detecting clinically unrecognized small subendocardial myocardial infarctions that do not result in wall motion abnormality or ECG changes, thereby identifying patients at risk of cardiac events.
- •CMR infarct imaging can provide direct information on the amount of irreversibly injured myocardium and viable myocardium, including the extent of periinfarct zone and microvascular obstruction, which are strong predictors of cardiovascular outcome in patients after myocardial infarction (MI).
Case: A 54-year-old woman without significant risk factors for coronary artery disease presented to our services complaining of a 4-week history of exertional dyspnea (NYHA class III) and pedal edema. The patient did not have any history of alcoholism, family history of heart disease, or sudden cardiac death. ECG showed sinus rhythm and a left bundle branch block pattern of unknown duration. Transthoracic echocardiography showed a dilated left ventricle and severe global hypokinesis with reduced ejection fraction of 25%. A coronary angiography was performed that revealed no significant coronary stenosis. CMR was performed .
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- A, Electrocardiogram demonstrating sinus rhythm and left bundle branch block conduction. B, Cine CMR. Diastolic frames of mid short-axis and 2-chamber long axis cine steady-state free precession (SSFP) imaging which demonstrate moderately dilated left ventricular (LV) chamber and severe global hypokinesis. C, Contrast-enhanced CMR. Left panel shows absence of perfusion defects during first-pass gadolinium transit across the myocardium. Right panel shows a mid short-axis late enhancement (LGE) image obtained 10 minutes after gadolinium administration demonstrating midwall linear LGE, which are not confined to a coronary arterial distribution.
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