The study group consisted of 2,123 patients— 1,201 Caucasian patients and 922 African-American patients—attending the hospital as both inpatients, outpatients, and the emergency department. These patients had an ECG recorded as part of their examination, and they were divided according to patient age into 10-year groups beginning at the third decade of life and extending through the 10th decade of life. ECGs recorded between October 28, 1996 and June 30, 1998 were retrieved from the files of the Carter Smith, Sr. ECG Laboratory of the hospital in groups of 95 to 250 ECGs for each age group of both African-American and Caucasian patients. The number of patients in each age group varied because of differing numbers of patients in the study groups attending the hospital but averaged 115 for African-American patients (range: 43-167) and 150 for Caucasian patients (range: 104-181). Each group of ECGs was studied in a consecutive manner. When a series of ECGs were recorded on a patient, the earliest ECG was chosen as the one of study. All ECGs were recorded with the patient supine using the computer programs of the Marquette Electronic MAC8 Resting ECG Analysis system at a paper speed of 25 mm/s, and the author reviewed all ECG interpretations. Correlation of the patient’s ECG and hospital diagnosis was not within the scope of this study. All calculations of the prevalence of first-degree AV block were rounded off to the nearest 10th of a percent.
Standard definitions of first-degree AV block were used throughout the study, and the lead with the longest PR interval, usually lead II, was employed for the study. First-degree AV block is defined as occurring in a patient with sinus rhythm and a PR interval of 210 ms or greater. Seven patients were excluded from the study: three with complete AV block, two with second-degree AV block, and two with second-degree sino-atrial block. The results of the present study are compared with data from population-based surveys.
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Pearson’s % (Chi-squared) test was used to compare differences in the prevalence of AV block in various groups. A p value of <0.05 is considered statistically significant.