EFFECT OF NOISE ON IDENTIFICATION OF VENTRICULAR LATE POTENTIALS

Abstract

Objective: To determine the effect of noise on identification of ventricular late potentials.

Study Design: Cross sectional comparative study.

Place and Duration of Study: Armed Forces Institute of Cardiology/National Institute of Heart Diseases, Rawalpindi from May 2006 to February 2007.

Methodology: The study included 37 patients with Mitral Valve Prolapse for the identification of ventricular late potentials. Patients with acute or old myocardial infarction, diabetes mellitus and systemic hypertension were excluded from the study. Signal averaged ECG was recorded according to the standard protocol. On the basis of noise level, the patients were divided in two groups i.e. low noise group (<0.20 μv) and high noise
group (0.20μv).

Results: Sixteen patients were in low noise group and 21 were in high noise group. Frequency of patients with ventricular late potentials was significantly higher in low noise group as compared to the high noise group i.e. 44% vs 10% (p-value 0.02). Mean values of noise and SAECG parameters were also significantly different between low and high noise groups. Noise was significantly correlated with the durations of filtered QRS complex and low amplitude signal below 40μv but not with the root mean square voltage of signal in the last 40ms of filtered QRS complex.

Conclusion: Ventricular late potentials are noise dependent and the probability of their identification increases at reduced noise levels.