MRI in nonischemic acquired heart disease

[Myocarditis: magnetic resonance imaging diagnosis and follow-up]

Myocarditis, inflammation of the myocardium, is usually due to viral infection. Diagnostic confirmation in ordinary clinical practice is difficult because the findings on the clinical history, physical examination, electrocardiogram, and laboratory tests offer scant diagnostic accuracy, and the differential diagnosis is often done with acute myocardial infarction. Cardiac magnetic resonance imaging (CMR) has become the method of choice for the diagnosis of myocarditis. In this article, we describe the CMR findings at diagnosis and during the follow-up of patients with myocarditis, the differential diagnosis with other acute processes like myocardial infarction, and the prognostic factors studied with CMR.

Hemodynamic aspects of mitral regurgitation assessed by generalized phase-contrast MRI

PURPOSE

To investigate the utility of MRI measurement of left atrial (LA) flow patterns and turbulent kinetic energy (TKE) in patients with clinically significant mitral regurgitation.

MATERIALS AND METHODS

Three-dimensional cine phase-contrast MRI (PC-MRI) data were acquired in five patients with posterior mitral leaflet prolapse and two normal volunteers. LA flow patterns were assessed using particle trace visualization. Specifically, vortices were recognized by closed streamlines. LA flow distortion was assessed by estimation of TKE. In addition, the regurgitant volume was measured.

RESULTS

Four of the mitral regurgitation patients had eccentric regurgitant jets directed toward the septum; one patient had a central jet. The dominant systolic vortex was located in proximity to the regurgitant jet. The LA flow was highly disturbed with elevated values of TKE; peak LA TKE ranged from 13 to 37 mJ and occurred consistently at late systole. The average LA TKE per cardiac cycle was significantly related to the regurgitant volume (TKE = 0.573 + 0.179·RegVol, R(2) = 0.983).

CONCLUSION

MRI permits investigations of atrial flow patterns and TKE in significant mitral regurgitation. The degree of LA flow distortion, as measured by the average LA TKE over one cardiac cycle, appears to reflect the severity of regurgitation.

MRI of nonischemic cardiomyopathy

OBJECTIVE

The purpose of this article is to present current clinical and research issues in MRI evaluation of nonischemic cardiomyopathy, a diverse set of diseases, many of which have a genetic basis.

CONCLUSION

Cardiac cine MRI along with delayed myocardial enhancement MRI and other MRI techniques can provide information beyond echocardiography for tissue characterization. MRI is increasingly being used for evaluation of genetically positive, phenotypically negative patients as well as for risk stratification.

Clinical characteristics and role of early cardiac magnetic resonance imaging in patients with suspected ST-elevation myocardial infarction and normal coronary arteries

A variety of conditions other than acute myocardial infarction may cause ST-elevation. Our objective was to evaluate the impact of cardiac magnetic resonance (CMR) on differential diagnosis from a prospective series of patients with suspected ST-elevation myocardial infarction (STEMI) and completely normal coronary arteries. Among 1,145 patients with suspected STEMI, 49 patients had completely normal coronary arteries and entered a prospective registry. CMR was done within 24 h, if possible, and included function analyses, T2-weighted imaging (T2 ratio), T1-weighted imaging before and after gadolineum administration (global relative enhancement; gRE), and late gadolineum enhancement (LGE). All patients were asked for a follow-up CMR after approximately 3 months. The incidence of patients with suspected STEMI and normal coronary arteries was 4.3% and mean age was 45 ± 14 years (STEMI group 64 ± 13 years; P < 0.001). 55% had a recent history of infection. Cardiac biomarkers showed a moderate elevation on admission. There was a significant change from baseline to follow-up for LV end-diastolic volumes (EDV) (P < 0.001), LV mass (P < 0.05), mean T2 ratio (P < 0.05), and LGE volume (P < 0.05). Major diagnostic groups were myocarditis (29%), pericarditis (27%), and takotsubo cardiomyopathy (10%). 18% were regarded as non-diagnostic. The study showed an incidence of 4.3% of patients with suspected STEMI and completely normal coronary arteries. Early CMR was valuable in the evaluation of the differential diagnoses and to exclude myocardial abnormalities in patients with uncertain aetiology. Further studies are needed for the assessment of long-term outcome.

Applications of cardiac magnetic resonance in electrophysiology

Contemporary methods for evaluation and treatment of arrhythmia are increasingly dependent upon characterization of the underlying myocardial substrate. Cardiovascular magnetic resonance offers unsurpassed soft tissue resolution capable of visualizing detailed cardiac anatomic features and intra-myocardial barriers to conduction. Non-invasive visualization of such anatomic detail has the potential to improve methods to diagnose, risk stratify, and treat patients with arrhythmia. This review describes a brief overview of the current knowledge on the applications of cardiac magnetic resonance for evaluation and treatment of patients with arrhythmia.