s heart disease continues to bethe #1 cause of death in theUnited States, primary and secondaryprevention efforts warrant renewed at-tention. Silent myocardial ischemiaand silent MI, once believed relativelyrare, are now recognized to affect any-where from 21 to 68% of older adultswith coronary artery disease (CAD),or nearly 3 million Americans. Theserisk factors increase the incidence ofnew coronary events and death inolder adults and require aggressivepharmacologic treatment when dis-covered. The evidence supports peri-odic routine ECGs in all adults age≥60, but particularly before and aftersurgery.This article reviews the epidemiol-ogy, diagnosis, and treatment of silentischemia and silent MI in older adults.[Editor’s note: See pages 57 and 58 fora patient Action Plan for handlingheart attacks.]Silent myocardial ischemiaSilent or asymptomatic myocardial is-chemia may affect 33 to 49% of olderAmericans with CAD.1,2(Silent my-ocardial ischemia is defined as hori-zontal or downsloping ST-segment de-pression of 1.0 mm or more below thelevel at rest at 80 milliseconds after theJ point, lasting for 1.0 minute or longer,and unassociated with anginal symp-toms detected by 24-hour ambulatoryECGs.)The reason for the frequent absenceof chest pain in older patients with CADis unclear. Speculations include:3● cognitive impairment with in-ability to verbalize a sensation of pain● myocardial collateral circulationrelated to gradual progressive coronaryartery narrowing● a reduced sensitivity to pain be-cause of aging changes such as systemicor localized autonomic dysfunction.Ambepitiya et al compared the timedelay between the onset of 1 mm ofECG ST-segment depression and theonset of angina pectoris during exercisestress testing. Significantly, the meandelay was 49 seconds in patients aged70-82 compared with 30 seconds in pa-tients aged 42-59.4The investigatorspostulated that the delay in perceptionof myocardial ischemia in older patientsinvolved peripheral mechanisms suchas changes in the myocardial autonomicnerve endings with blunting of the per-ception of ischemic pain, as well aschanges in central mechanisms.In the older patient population, vaguesymptoms, such as unexplained dysp-nea, neurologic symptoms or GI symp-toms, warrant follow-up with an ECG.Prognosis of silent ischemiaOlder patients with silent myocardialischemia are twice as likely to have newcoronary events than older patientswith no myocardial ischemia.1,2At 45-month follow-up of 395 men, meanage 80, and at 47-month follow-up of771 women, mean age 81, with CAD,silent myocardial ischemia increased theCardiovascular diseaseCardiovascular diseaseOlder men and women with coronary artery disease and silentmyocardial ischemia detected by 24-hour ambulatory electrocardiograms(ECGs) have a higher incidence of new coronary events than those withno silent ischemia. The prevalence of clinically unrecognized MI detectedby routine ECGs in older persons varies from 21 to 68%. Atypicalsymptoms associated with acute MI in older persons include dyspneaand neurologic and GI symptoms, as well as chest pain. Older personswith clinically unrecognized MI have a similar or higher incidence of newcoronary events and mortality compared with those with recognized MI,which suggests that an aggressive diagnostic and therapeutic approachmay be beneficial in these patients.Aronow WS. Silent MI. Prevalence and prognosis in older patients diagnosed by routineelectrocardiograms. Geriatrics 2003; 58(Jan):24-40.Key words: MI • Myocardial ischemia • Silent ischemia • ECGs • Q-waveAWilbert S. Aronow, MDSilent MIPrevalence and prognosis in older patientsdiagnosed by routine electrocardiograms24 Geriatrics January 2003 Volume 58, Number 1Dr. Aronowis clinical professor ofmedicine, department of medicine,cardiology and geriatrics divisions,New York Medical College, Valhalla,NY, and adjunct professor of geriatricsand adult development, Mount SinaiSchool of Medicine, New York, NY. Disclosure: The author has no real orapparent conflicts of interest relat-ing to the content presented here.www.geri.comincidence of new coronary events (sud-den coronary death or MI) 2.1 times inmen and 2.1 times in women.1In anotherstudy, at 43-month follow-up of 39 men,mean age 68, with coronary artery dis-ease, silent myocardial ischemia increasedthe incidence of new coronary events 16.0times.2Reduction of silent myocardialischemia in older men and women withheart disease by beta blocker therapy withpropranolol significantly reduced the in-cidence of sudden cardiac death, totalcardiac death, and total mortality.4Prevalence of unrecognized MIAs with myocardial ischemia, some pa-tients with MI may be completelyasymptomatic or the symptoms maybe so vague that they are unrecognizedby the patient or physician as an acuteMI. Figure 1 shows the percent of Q-wave MIs in the Framingham HeartStudy that were clinically unrecognizedbut diagnosed by routine ECGs in dif-ferent age groups of men and ofwomen aged 45-94.6Table 1 shows the percent—22 to68%—of MIs that were clinically unrec-ognized in older patients but diagnosedby routine ECGs in other studies.7-14In a prospective study, ECGs andMB-isoenzymes of serum creatine ki-nase were obtained at the time of chestpain, sudden dyspnea, new neurologicsymptoms, and GI symptoms in 110older patients, mean age 82.9(Chest painwas defined as pain, tightness, pressure,or discomfort in the chest. Neurologicsymptoms as the presenting symptomof MI included syncope, stroke, tran-sient cerebral ischemic attack, faintness,and acute confusion. GI symptoms asthe presenting symptom of MI includedepigastric distress, nausea, and vomit-ing.) Of 110 Q-wave or non-Q-waveMIs, 23 (21%) were clinically unrecog-nized. Two of the clinically unrecognizedMIs (2%) occurred during surgery.9Inthe largest prospective study, involving4,315 patients age 50 and older under-going major elective non-cardiacsurgery, history of ischemic heart dis-ease, as evidenced by Q-waves on the ECGor clinical history of MI was 1 of 6 inde-pendent predictors of major cardiac com-plications.15These data indicate the im-portance of obtaining an ECG routinelybefore and after surgery and of obtaininga periodic routine ECG in older patients.Exercise stress testing. All older pa-tients with silent MI should have anexercise stress test performed for di-agnostic and prognostic reasons.15,16Exercise stress testing in these patientsshould evaluate:● symptoms that develop during
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