Eighty-six patients (73 men, 13 women; mean age 57 ± 12 years) with coronary artery disease and LV dysfunction (LVEF < 50%, mean LVEF was 26 ± 12%) scheduled to undergo either revascularization or medical therapy ± implantable cardiac defibrillator (ICD) placement were recruited consecutively for CMR. All patients underwent diagnostic coronary angiography before CMR examination. After CMR examination and assessment of total myocardial scar volume, all the patients were followed for the presence of cardiovascular events, as described below. 35 patients underwent revascularization (26 patients coronary artery bypass surgery (CABG) and 9 percutaneous coronary intervention (PCI) patients) ± ICD placement and 51 patients received medical therapy ± ICD placement. All patients had previous MI. But patients with acute infarction (within seven days), unstable angina pectoris, asthma, pulmonary disease, severe valvular disease, or contraindications to the CMR examination were excluded. The study protocol was approved by the human subjects committee at Stanford university.

All images were acquired on a 1.5-Tesla whole-body scanner (Signa, GE Healthcare, Milwaukee, WI) with the patient in a supine position using an 8-element phased-array radiofrequency coil with breath-holding and cardiac gating. Cine images of the LV in short and long axes were acquired using a steady-state free precession sequence (SSFP, TR 3.8, TE 1.6, FA 45°, slice thickness 10 mm, slice gap 0). Late gadolinium enhancement (LGE) images (segmented k-space inversion recovery sequence, TR 7.1, TE 3.1, TI 200–250, slice thickness 10 mm, slice gap 0) were acquired throughout the entire LV starting at 20 min, following administration of 0.2 mmol/kg of gadolinium diethytriaminepentaacetic acid (Gd-DTPA, Magnevist^®, Schering AG, Germany). The inversion time set to null the signal of normal myocardium after Gd-DTPA administration was adjusted during the course of the scan as necessary.

Images were analyzed using MASS analysis software (MASS Analysis Plus Version 5.1, Leiden University). Automatic tracing with manual adjustment of endocardial and epicardial borders from short-axis images was performed to calculate left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and LVEF.

The short-axis LGE images were evaluated for the presence of scar and traced manually to measure total scar volume. An infarct region was defined as an area of hyperenhancement, with a higher signal intensity (≥ 2 SD) compare to remote region in the same slice 13. Myocardial and scar volume were calculated (myocardial or scar area × slice thickness of 10 mm). The scar percentage of myocardial volume was also expressed as percentage of the total myocardial volume (scar volume/myocardial volume × 100) as shown in figure 1. We analyzed contrast-enhanced images using the 72-segment model in which the left ventricle was divided into 12 circumferential segments in six short-axis views 18. In patients with microvascular obstruction, these hypointense areas were included as scar area. Isolated midwall or subepicardial hyperenhancement was excluded because this was not considered as scar area 1920. The transmural extent of hyperenhancement was graded as a percentage of scar tissue in each segment: 0%, 1 to 25%, 26 to 50%, and 51 to 75% (non-transmural); and 76 to 100% (transmural).

Clinical characteristics of the study population are summarized in table 1. Thirty-five patients were revascularized (26 CABG, 9 PCI patients). Clinical follow-up over a period of 20 ± 16 months (minimum period was 1 month, maximum period was 56 months) was obtained in all patients. Twenty-four of the 86 patients (28%) had 2 vessel disease (left main, or two vessel with proximal left anterior descending artery), and 49 patients (57%) had 3 vessel disease. During the follow-up period, 33 patients (38%) had cardiovascular events (mean follow-up period was 20 ± 16 months). Fifteen patients of the 33 patients had CHF, 9 patients had ventricular arrhythmia, 2 patients had syncope, 2 patients had MI, 5 patients needed revascularization and 6 patients died due to cardiovascular cause during the follow-up period. There were any deaths or events were related to revascularization procedures.

CMR parameters among the patients ± cardiovascular events are summarized in table 2. Both mean scar volume and scar percentage of the myocardium were larger in patients with cardiovascular events than those without cardiovascular events (16.8 ± 12.4 cm3 vs. 11.7 ± 12.6 cm3, p = 0.023 and 10.2 ± 6.9% vs. 7.2 ± 6.7%, p = 0.037, respectively). There were no significant differences in LVEDV, LVESV and LVEF between the patients with and without cardiovascular events (234 ± 76 ml vs. 230 ± 88 ml, 180 ± 73 ml vs. 175 ± 90 ml, 25 ± 10% vs. 27 ± 13%, respectively).

The transmurality of the scar was also analyzed by dividing into non-transmural vs. transmural extent of MI (1–75% vs. 76–100%, respectively) among the patients as shown in table 3. Patients with cardiovascular events had larger number of non-transmural segments than patients without cardiovascular events (18.4 ± 14.0% vs. 13.8 ± 11.2%, p = 0.049). Specifically, higher incidences of cardiovascular events were seen in the 26–50% non-transmural segments (9.2 ± 10.6% vs. 3.2 ± 3.6%, p = 0.03). In subanalysis, there were no significant difference in the number of both non-transmural segments and transmural segment in patients with and without ventricular arrhythmia (p = 0.71, p = 0.64, respectively). In addition, there were no significant difference in the number of both non-transmural segment and transmural segment in patients with and without worsening CHF (p = 0.94, p = 0.06, respectively).

The correlation of LVEF, LVEDV and LVESV with scar volume and scar percentage of the myocardium is shown in figure 2, 3, 4 (figure 2: LVEF, figure 3: LVEDV, figure 4: LVESV). These measurements did not correlate with scar volume with r values of 0.16, 0.08 and 0.10, respectively and did not correlate with scar percentage of the myocardium with r values of 0.08, 0.01 and 0.02, respectively.

When the patients were analyzed between the revascularization (CABG or PCI ± ICD placement) and the no revascularization groups (medical therapy ± ICD placement), there were more patients with 3 vessel disease and with ICD placement who underwent revascularization (p = 0.02, for each) as shown in table 1. However, there was no significant difference in both scar volume and percentage of the myocardium between the 2 groups (p = 0.60 and 0.37, respectively). Finally, there was no significant difference in the incidence of cardiovascular events between these two groups (p = 0.24).

Analyses of clinical characteristics of all patients with and without cardiovascular events are summarized in table 4. There was no significant difference in clinical parameters between these two groups.