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).



KEY POINTS




Case 1


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 ( Figure 10-1 ).




Figure 10-1


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.


Nonischemic Cardiomyopathy


Comments


Determining the etiology of heart failure is essential for directing the correct treatment and predicting survival of patients who presented with new cardiac failure. CMR can often differentiate ischemic from nonischemic etiologies by the pattern of distribution of LGE. Indeed, in patients with idiopathic nonischemic cardiomyopathy, there is often a distinct pattern of LGE presenting as patchy longitudinal midwall LGE that spares the subendocardium and subepicardium and does not conform to a coronary vascular territory, as in our current case. The transmural extent of this midwall LGE has been implicated in the pathogenesis of ventricular arrhythmias in patients with nonischemic dilated cardiomyopathy. More recently LGE has been shown to prognosticate cardiac events in patients with this condition.




Case 2


A 48-year-old woman without coronary risk factors was admitted to the emergency room following 30 minutes of severe retrosternal discomfort associated with diaphoresis. ECG showed widespread T-wave inversion in anterolateral leads. Emergency cardiac catheterization revealed unobstructed epicardial coronary arteries with LV distal akinesis resembling apical ballooning but without any intracavitary thrombus formation. CMR was performed the following day to assess the degree of ventricular dysfunction ( Figure 10-2 ).




Figure 10-2


A, ECG. Sinus rhythm with marked and widespread symmetrical T wave inversion in anterolateral (V1 to V6) chest leads. B, Coronary angiogram. Unobstructed left and right epicardial coronary arteries. C, CMR cine SSFP imaging. Four-chamber and two-chamber long-axis SSFP showing distal septal and apical left ventricular thinning and systolic ballooning. D, Contrast-enhanced CMR. Short-axis myocardial perfusion after first pass gadolinium ( left upper ) showing no significant perfusion defects to suggest coronary flow impedance. Mid short-axis ( right upper ) and long-axis ( lower panel ) LGE imaging at 10 minutes after gadolinium (0.15 mmol/kg) injection showing no evidence of distal segmental or apical infarction.


Takotsubo Cardiomyopathy




Comments


Left ventricular (LV) apical ballooning (Takotsubo cardiomyopathy) is a unique clinical entity characterized by transient anteroapical hypokinesis in the setting of elevated adrenergic tone, ECG abnormalities mimicking acute coronary syndrome, modest elevation of cardiac enzyme levels, and a lack of angiographically significant epicardial coronary stenoses. Although diagnosis is usually suspected by a lack of significant coronary lesion on angiography, CMR is useful in this context by providing precise evidence of LV structural changes, exclusion of concomitant significant obstructive coronary disease, assessing for any extent of myocardial necrosis, and noninvasive monitoring for recovery of ventricular function.




Case 3


A 56-year-old man with a history of anterior myocardial infarction one year ago was referred to CMR for assessment of new onset chest pain, ventricular function, and myocardial viability ( Figure 10-3 ). During the hospitalization for his acute MI, coronary intervention of the proximal LAD was complicated with luminal dissection and as a result there was incomplete coronary revascularization of the infarct-related artery despite attempts to perform coronary stents.




Figure 10-3


A, Resting ECG showing sinus rhythm, and evidence of old anterior MI by Q waves in leads V1 to V4 with inverted T waves. B, Cine SSFP imaging demonstrating a large region of anterior akinesia involving the mid to distal anterior walls (top images show the end-diastolic frames and the bottom images show the end-systolic frames of the short-axis and two-chamber long axis views, respectively). Despite the anterior MI, there is normal global LV size (81 ml/m 2 ) and only mildly reduced LV ejection fraction of 51%. C, This anterior akinesia is matched by a medium-sized late enhancement consistent with a transmural MI in short-axis and long-axis views, respectively. Using a semi-automated signal intensity detection technique, the infarct size is quantified at 15% of the total LV mass. D, First-pass myocardial perfusion using fast gradient-echo CMR: Comparison between rest ( left image ) and during adenosine stress ( middle image ), there is marked reversibility of the perfusion defect, which involved the anterior, anteroseptal, and even the inferoseptal wall, which is not infracted (compare with the right image of late enhancement). These findings suggest evidence of periinfarct ischemia surrounding a medium-sized MI. This patient on repeat coronary angiography showed a subtotally occluded proximal left descending artery with collateral supply from the right coronary artery.

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Feb 1, 2019 | Posted by in MAGNETIC RESONANCE IMAGING | Comments Off on Dilated Cardiomyopathy and Myocardial Infarction
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