Methods

We collected 142 electrocardiograms (ECGs) with dates ranging from March 2, 2008 to April, 13 2011 from the ones sent for routine reading at the St. Luke's Episcopal Hospital ECG laboratory and read by one investigator (YB). ECGs showing diffuse ST segment depression in > 7 leads with ST-segment elevation in aVR were collected. Patients with left bundle branch block, QRS duration of > 130 msec, ventricular rhythm or ventricular paced rhythm were excluded. The polarity of the T waves in the leads with maximal ST depression was defined as positive if the terminal part of the T wave was > 0.1 mV above the isoelectric line, or negative.

Demographic data, date of ECG, the indication for the ECG, presence of elevated cardiac markers, diagnosis of cardiac conditions (non-ST elevation acute coronary syndrome [NSTE-ACS], non-ischemic dilated cardiomyopathy [NIDCM], ischemic cardiomyopathy, hypertrophic obstructive cardiomyopathy and hypertensive heart disease, and significant valvular disease), performance of coronary angiography (if so, number of diseased vessels [> 70% diameter stenosis] and presence of left main stenosis > 50%), performance of revascularization (percutaneous intervention [PCI] or CABG) following the ECG and the existence of previous ECG (> 24 hours) with the same pattern or without this pattern were obtained from the patients' medical records. Angiographic data were broken up into LMCA, LMEQ disease or three-vessel disease (3VD), two-vessel disease (2VD), one-vessel disease (1VD) or no significant coronary artery narrowing. If the patients were post-CABG and the grafts to the left anterior descending (LAD) and/or obtuse marginals were patent we did not list them as LMCA or LMEQ disease. The ECG patterns were classified as chronic (present for at least 24 hours prior to selected ECG), dynamic (more significant changes or new pattern) or no prior ECG obtained.

Results

Out of the 142 patients that were chosen for our study, 9 (6.3%) had insufficient data. Of the remaining 133 patients, 57 (43%) underwent coronary angiography (CA) (Table 1).

Demographic and clinical characteristics of the patients are shown in Table 1. The prevalence of men was higher among patients undergoing CA than among those who did not undergo CA; however, there was no difference in mean age or race. The chief indication for the ECG was chest pain in more than half of the patients that underwent CA compared to only 20% in the group without CA. There were no differences between the groups in the percentage of patients having ECG for shortness of breath, palpitations or arrhythmia, syncope, heart failure or abdominal pain. ACS was clinically suspected in 83% of the patients who underwent CA and in only 50% of the patients who did not undergo CA. The pattern of diffuse ST depression with ST elevation in lead aVR was chronic in 30% and 26% of the patients who underwent or did not undergo CA, respectively. Dynamic changes were noted in 44% and 53%, respectively (Table 1). A quarter of the patients in each group had ECG criteria for LVH. There were no significant difference in the prevalence of intraventricular conduction delay [incomplete right bundle branch block (incRBBB), complete right bundle branch block (RBBB), nonspecific intraventricular conduction delay (IVCD) or incomplete left bundle branch block (incLBBB)] among groups. Interestingly, the majority of the patients (93%) in the CA group had positive T waves, whereas only 60% of the patients who did not undergo CA had positive T waves (Table 1).

At discharge, ACS was diagnosed in 34 patients (60%) who underwent CA and in only 3 (4%) patients who did not undergo CA (p<0.00001).

Medical diagnoses that were associated with the ECG pattern are listed in Table 2. As mentioned above, only 37 (28%) patients were diagnosed with NSTE-ACS. Almost half of the patients had hypertensive heart disease.

Among the 57 patients that underwent CA, 24 (42%) had a history of diabetes mellitus, 46 (81%) had hypertension, 39 (68%) had known coronary artery disease and 21 (37%) had known cardiomyopathy. Twenty-two patients (39%) had prior CABG and 19 (33%) had a history of prior PCI. A total of 38 (67%) of the patients that underwent CA presented with either chest pain or shortness of breath; 22 (58%) of these patients were diagnosed with NSTE-ACS; 4 (9.1%) developed ST elevation myocardial infarction later on during their hospitalization. Angiographic results of the patients that underwent CA are listed in Table 3. Of note, 15 (26%) of these patients had normal coronary arteries or no significant coronary artery disease, while only 10 (18%) had LMCA narrowing, 3 (5%) patients had LMEQ disease, and 10 (18%) had 3VD. Thus, three vessel disease, LMCA or LMEQ was present in only 23 patients (40%). Significant left anterior descending narrowing (> 70% luminal diameter stenosis) was detected in 22 patients (39%), significant left circumflex artery narrowing in 19 patients (33%), significant right coronary artery narrowing in 24 patients (42%). One patient with prior CABG had > 70% luminal narrowing of the left internal mammary artery and 6 had significant narrowing of saphenous vein grafts. A total of 29 patients (51%) needed revascularization, with 14 (25%) undergoing PCI and 16 (28%) undergoing CABG, while the other half were either treated medically or underwent a different procedure, such as septal ablation for hypertrophic obstructive cardiomyopathy.

CA results of the 35 patients that did not have prior CABG are also listed in Table 3. A total of 12 (34%) of these patients had normal coronary arteries or no significant coronary artery disease, while only 7 (20%) had LMCA narrowing, 3 (9%) had LMEQ disease, and 5 (14%) had 3VD. Thus, 15 patients (43%) had three vessel disease, LMCA or LMEQ, without a significant difference from the whole group. Sixteen patients (46%) needed revascularization (6 patients (17%) underwent PCI and 10 (29%) CABG), while the rest (54%) were treated either medically or underwent a different procedure.

In 34 patients who underwent CA (60%), the initial presentation was suspicious of ACS. The prevalence of LMCA, LMEQ or three vessel disease was comparable to that of the whole group (Table 3). As expected, more patients presented with ACS underwent revascularization (74%), with 41% undergoing PCI and 35% CABG.

Among the patients that underwent CA, 43 patients (75%) did not have ECG criteria for LVH. There were no significant differences in the prevalence of LMCA, LMEQ or three vessel disease between patients without LVH criteria and the whole group (Table 3). Among the patients without LVH, 22 (51%) underwent revascularization with 26% undergoing PCI and 28% CABG.