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. 2005 Nov 1;112(18):2821-5.
doi: 10.1161/CIRCULATIONAHA.105.549659.

Magnetic resonance assessment of the substrate for inducible ventricular tachycardia in nonischemic cardiomyopathy

Saman Nazarian  1 , David A Bluemke, Albert C Lardo, Menekhem M Zviman, Stanley P Watkins, Timm L Dickfeld, Glenn R Meininger, Ariel Roguin, Hugh Calkins, Gordon F Tomaselli, Robert G Weiss, Ronald D Berger, João A C Lima, Henry R Halperin
Affiliations

Magnetic resonance assessment of the substrate for inducible ventricular tachycardia in nonischemic cardiomyopathy

Saman Nazarian et al. Circulation. .

Abstract

Background: Patients with left ventricular dysfunction have an elevated risk of sudden cardiac death. However, the substrate for ventricular arrhythmia in patients with nonischemic cardiomyopathy remains poorly understood. We hypothesized that the distribution of scar identified by MRI is predictive of inducible ventricular tachycardia.

Methods and results: Short-axis cine steady-state free-precession and postcontrast inversion-recovery gradient-echo MRI sequences were obtained before electrophysiological study in 26 patients with nonischemic cardiomyopathy. Left ventricular ejection fraction was measured from end-diastolic and end-systolic cine images. The transmural extent of scar as a percentage of wall thickness (percent scar transmurality) in each of 12 radial sectors per slice was calculated in all myocardial slices. The percentages of sectors with 1% to 25%, 26% to 50%, 51% to 75%, and 76% to 100% scar transmurality were determined for each patient. Predominance of scar distribution involving 26% to 75% of wall thickness was significantly predictive of inducible ventricular tachycardia and remained independently predictive in the multivariable model after adjustment for left ventricular ejection fraction (odds ratio, 9.125; P=0.020).

Conclusions: MR assessment of scar distribution can identify the substrate for inducible ventricular tachycardia and may identify high-risk patients with nonischemic cardiomyopathy currently missed by ejection fraction criteria.

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Figures

Figure 1
Figure 1
Analysis of delayed enhancement images. A, The myocardial slice has been divided into 12 radial sectors per slice, and the left ventricular endocardium, epicardium (white contour), and midwall area of scar (red contour) have been contoured. B, Thirty radial lines drawn from the epicardium to the endocardium in 1 sector (inset). C, The proportion of each line that intersected scar was computed by dividing the length of segment a by b for each line. The transmural extent of scar in each sector was then determined by calculating the average scar transmurality of all 30 lines per sector.
Figure 2
Figure 2
Typical contrast-enhanced images obtained by MRI. Scar involvement was most common in the basal myocardial slices. The myocardium has been divided into 12 sectors, starting from the posterior right ventricular insertion point (red line). A, Example of myocardium free of scar. B, Small region of hyperenhancement as an example of predominant scar distribution involving 1% to 25% of wall thickness. Sector numbering is clockwise, starting from the right ventricular insertion point, with sectors 3 to 5 having 4%, 20%, and 17% scar. C, An example of predominance of scar involving 26% to 75% of wall thickness. Sectors 1 to 8 have 50%, 56%, 53%, 61%, 62%, 71%, 40%, and 11% scar; sector 12 has 40% scar. C, The midwall area of hyperenhancement was visualized using a range of inversion times and in multiple planes. D, Example of scar involving 76% to 100% of wall thickness (sectors 11 and 12 with 85% and 78% scar).
Figure 3
Figure 3
Example of the relation between scar location on delayed enhancement images and morphology of ventricular tachycardia on 12-lead ECG. A, A 4-chamber image of the heart, with the right atrium and ventricle at the top of the image and left atrium and ventricle at the bottom. B, The left bundle branch–like configuration in lead V1 of the ventricular tachycardia ECG suggests an exit site in the right ventricle or interventricular septum and is compatible with the scar location in A.
Figure 4
Figure 4
Histogram illustrating median sector involvement in each level of hyperenhancement (scar) transmurality in patients stratified by inducibility at electrophysiological study. Bars represent median±interquartile range. Wilcoxon rank-sum comparisons are reported above the bars. Sectors without hyperenhancement are not shown. The median percent of sectors without hyperenhancement was 98% (interquartile range, 89 to 100) in the noninducible subgroup of patients vs 81% (interquartile range, 75 to 81) in patients with inducible ventricular tachycardia at electrophysiological study (P=0.011).
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