Usefulness of silent myocardial ischemia detected by ambulatory electrocardiographic monitoring in predicting new coronary events in elderly patients

BRIEF REPORTS

Usefulness of Silent Mvocardial Electrocardiographic Monitoring in Elderly Patients Wilbert S. Aronow,

MD,

and Stanley Epstein,

lschemia Detected by Ambulatory in Predicting New Coronary Events MD

nrecognizedmyocardial infarction (MI) detectedby electrocardiogram (ECG) occurred in 83 of 237 U women (35%) and 130 of 469 men (28%) with initial MI in the Framingham study.’ Unrecognized MI had as serious a prognosis as recognized MI in that study.’ In our 1985 study,=we reported that unrecognizedQ-wave MI detected by ECG occurred in 78 of 115 elderly patients (68%) with MI in a long-term health care facility. After instructing staff physicianson the different presenting symptomsof MI in elderly patients, the incidence of unrecognizedMI detectedby ECG in a prospectivestudy was 23 of 110 MIS (21%).3 Silent myocardial ischemia detected by ambulatory ECG monitoring is common during daily life in asymptomatic patients with coronary artery disease(CAD) and positive treadmill exercisetests4 In unstableangina, 80% of ischemicepisodesare silent5 Abnormalities in regional and global left ventricular wall motion are similar in patients with CAD, with and without silent ischemia.6 Rubidium-82 positron-emission tomographic studies have demonstratedreducedmyocardial perfusion during episodesof silent myocardial ischemiadetectedby ambulatory ECG monitoring in patients with CAD.’ The prognosis of asymptomatic silent ischemia in patients with CAD dependson the extent of CAD and left ventricular dysfunction8 The prognostic value of silent ischemia detected by ambulatory ECG monitoring has been reported in patients with unstable angina,9-1’in high-risk postinfarction patientsi and in patients with stable CAD.13J4We performed a prospectivestudy (1) to determine the prevalence of silent ischemia in elderly patients with CAD, patients with systemic hypertension, valvular heart diseaseor cardiomyopathy, and in patients with no evidence of heart disease,and (2) to correlate silent ischemiawith cardiac eventsat 26-month follow-up in these groups of patients. Ambulatory ECG monitoring was performed for 24 hours using portable Avionics tape recorders (model 44.5) to obtain 2 leads corresponding to a modified VI and VS. The tapes were analyzed using a CardioData Mk 3 computer system. ST-segment changes were written out on ECGpaper at a speed of 25 mm/s and interpreted by an experienced cardiologist. Patients with marked resting ST-segment depression were excluded from the study. Recordings were satisfactory in 626patients (84% from original group). The 626 patients included 457 women and I69 men, mean age 82 f 8 years (range 62 to 101). Silent ischemia was diagnosed if horizontal or downslopingST-segment depression LI .Omm below the From the Hebrew Hospital for Chronic Sick, 2200 Givan Avenue, Bronx, New York 10475. Manuscript received June 3, 1988; revised manuscript received and accepted July 27, 1988.

TABLE I Prevalence of Silent lschemia in Elderly Patients With Coronary Artery Disease, Patients With Hypertension, Valvular Heart Disease or Cardiomyopathy, and Patients Without Heart Disease

Coronary artery disease Hypertension, valvular disease or cardiomyopathy No heart disease

Silent lschemia (n)

(“h)

62/185

34

51/349

15

5/92

5

resting level occurred at 80 ms after the J point, lasted for I1 .O minute and was unassociated with angina1 symptoms. If resting ST-segment depression occurred, an additional 2.0 mm of ischemic ST-segment depression below the resting level at 80 ms after the Jpoint was required. Patients were considered at study entry to have CAD if they had a documented clinical history of MI, ECG evidence of Q-wave MI, or angina. A systolic bloodpressure 2 160 mm Hg on 3 occasions was considered systolic hypertension and a diastolic blood pressure 190 mm Hg on 3 occasions was regarded as diastolic hypertension.t5 Mean follow-up was 26 f 6 months (range 8 to 34). New cardiac events were diagnosed if the patient developed documented nonfatal or fatal MI, primary ventricular fibrillation or sudden cardiac death. MI was documented as previously described.3 Primary ventricular fibrillation was defined as ventricular fibrillation documented by ECG in a clinically stable patient with cardiac disease unexpectedly having new cardiovascular symptoms. Sudden cardiac death was defined as a patient with cardiac disease unexpectedly beingfound dead within 1 hour of being clinically stable.t6 In some cases of sudden cardiac death, the patients died within minutes after the appearance of new cardiovascular symptoms and before an ECG could be taken. Chi-square analyses were used to analyze data. Table I lists the prevalence of silent ischemia in elderly patients with CAD, in patients with systolic or diastolic hypertension, valvular heart disease or cardiomyopathy without CAD, and inpatients with no evidence of heart disease. In 118patients with silent ischemia, 294 episodes of silent ischemia occurred (2.5 episodes per patient per day). During a 26-month follow-up, new cardiac events occurred in 154 of 626 patients (25%). Table II lists the incidence of cardiac events correlated with silent ischemia in patients with CAD, in patients with systolic or diastolic hypertension, valvular heart disease or cardiomyopathy without CAD, and inpatients with no evidence of heart disease. Table II also lists the levels of statisti-

THE AMERICAN JOURNAL OF CARDIOLOGY DECEMBER 1, 1988

12%

BRIEF REPORTS

Our data showed that silent ischemia detected by ambulatory ECG monitoring waspresentin 34%of elderly patients with stable CAD, in 15%of elderly patients with systemichypertension,valvular heart diseaseor car# diomyopathy with no evidence of CAD, and in 5% of New Cardiac Events elderly patients with no evidenceof heart disease.PaNo Silent tients with systemichypertension may have silent ischeSilent lschemia lschemia mia due to associatedCAD. Systemichypertensionwith 09 Vd 04 (%) left ventricular hypertrophy may cause subendocardial ischemia due to hypertrophied myocardium, prolonged Hypertension, valvular disease systole,decreasedfunctional coronary artery reserveand increasedmyocardial oxygen demand. Silent myocardial ischemia significantly correlated with new cardiac eventsin our elderly patientswith stable CAD (p 60 minutes per day, in 3 of 10 patients (30%) artery disease. Am J Cardiol 1987:59:746-749. with silent ischemia persisting <60 minutes per day and 5. Nademanee K, Intnrachot V, Singh PN, Josephson MA, Singh BN. Characteristics and clinical significance of silent myocardial ischemia in unstable angina. in 1 of 19 patients (5%) without silent ischemia. J Cardiol 1986;58:26B-338. Gottlieb et al’* also showedthat silent ischemia de- 6.Am Cohn PF, Brown EJ Jr, Wynne JA, Hohnan BL, Atkins HL. Global and tected by ambulatory ECG monitoring was associated regional left ventricular ejection fraction abnormalities during exercise in patients with an adversel-year prognosisin high-risk postinfarc- with silent myocardial ischemia. JACC 1983:1:931-933. EC, Rocco MB, Selwyn AP. Characteristics and significance of ischetion patients. At l-year follow-up, death or myocardial 7.miaNabel detected by ambulatory electrocardiographic monitoring. Circulation 1987; infarction occurred in 11 of 30 patients (37%) with ische- 75(suppl V)3:!‘74- V83. Cohn PF. Detection and prognosis of the asymptomatic patient with silent mia comparedwith 8 of 73 patients (11%) without myo- 8.myocardial ischemia. Am J Cardiol 1988;61:4&6B. cardial ischemia. 9. Gottlieb SO, Weisfeldt ML. Ouyang P, Mellits ED, Gerstenblith G. Silent Stern and Tzivoni13 demonstrated by ambulatory ischemia as a marker for early unfavorable outcomes in patients with unstable N Engl J Med 1986;314:1214-1219. ECG monitoring in 80 patients with typical or atypical angina. 10. Gottlieb SO, Weisfeldt ML, Ouyang P, Mellits ED, Gerstenblith G. Silent angina pectoristhe presenceof myocardial ischemiain 37 ischemia predicts infarction and death during 2 year follow-up of unstable angina. patients. At 6- to 12-month follow-up, clinical symptoms JACC 1987:10:756-760. 11. Nademanee K, Intarachot V, Josephson MA, Rieders D, Mody FV, Singh worsenedin 16 of 37 patients (43%) with ischemiacom- BN. Prognostic significance of silent myocardial ischemia in patients with unstapared with 3 of 43 patients (7%) without ischemia.Stern ble angina. JACC 1987;10:1-9. 12. Gottlieb SO, Gottlieb SH, Achuff SC, Baumgardner R, Mellits ED, Weiset all4 showed by ambulatory ECG monitoring during feldt ML, Gerstenblith G. Silent ischemia on Halter monitoring predicts mortality daily activities that at 2-year follow-up, 23 of 76 patients in high-risk postinfarction patients. JAMA 1988;259:1030-1035. (30%) with prior MI with myocardial ischemiahad cardi- 13. Stern S, Tzivoni D. Early detection of silent ischemic heart disease by 24-hour monitoring of active subjects. Br Heart J 1974;36:481-486. ac eventscomparedwith 15 of 135 patients (11%) with ECG 14. Stern S, Gavish A, Zin D, Tzivoni D. Clinical outcome of silent myocardial prior MI without ischemia. Twenty-six of 86 patients ischemia. Am J Cardiol 1988;61:16F-18F. (30%) with no previous MI with ischemia had cardiac 15. Joint National Committee on Detection, Evaluation and Treatment of High Pressure. The 1988 report. Arch Intern Med 1988;148:1023-1038. events compared with 8 of 59 patients (14%) with no Blood 16. Roberts WC. Sudden cardiac death: definitions and causes. Am J Cardiol 1986:S7:1410-1413. previous MI and no ischemia. I

TABLE II Correlation of Silent lschemia With New Cardiac Events in Patients With Coronary Artery Disease, Patients With Hypertenaon, Valvular Heart Disease or Cardiomyopathy, and Patients Without Heart Disease

~‘r:

1296

THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 62