Abstract 3087: Candidates for Primary Prevention of Sudden Death with Ischemic Cardiomyopathy have Frequent and Asymptomatic Dynamic ST Segment Changes on Ambulatory 12-lead ECG Monitoring
Background: Myocardial ischemia is an important risk factor for sudden cardiac death (SCD) in patients with ischemic cardiomyopathy. However, many of these patients are commonly excluded from ambulatory ECG monitoring trials because of baseline electrocardiographic (ECG) abnormalities. This study was designed to characterize the ambulatory 12-lead ECG monitoring in unselected patients with ischemic cardiomyopathy who are candidates for primary prevention of SCD.
Methods: Patients with ischemic cardiomyopathy eligible for a prophylactic ICD underwent 24-hour ambulatory monitoring with a high resolution (1000 Hz sampling) 12-lead ECG (Mortara, Milwaukee WI). Analysis was performed blinded to all clinical data.
Results: Patients (n = 81) had NYHA Class 2.4 ± 0.7 heart failure symptoms and were on standard medical therapy (β-blockers - 88%, ACEI/ARB - 80%, statins - 79%). The resting heart rate was 69 ± 8 bpm, with average minimum and maximum of 51 ± 9 and 122 ± 17 bpm, respectively. Most patients were in sinus rhythm, however a majority had a wide QRS complex (n=43, 53%). Nonsustained ventricular arrhythmias occurred in 36 (44%). Despite the fact that no patient recorded anginal symptoms, dynamic ST segment deviation (depression or elevation) of at least 100 μV in ≥2 contiguous leads was present in 37 (46%). This included all 26 patients with a left bundle branch block or ventricular pacing, in whom ST segment analysis would not be routinely performed.
Conclusion: As expected, these ICD candidates with ischemic cardiomyopathy frequently had conduction abnormalities and ventricular arrhythmias. However, dynamic ST segment deviation consistent with acute myocardial ischemia was frequent and asymptomatic, especially among patients who would be excluded from monitoring trials. Since myocardial ischemia is an important risk factor for cardiac mortality and SCD in these patients, the exclusion of patients with baseline ECG abnormalities from ambulatory monitoring trials should be reconsidered.