Prevalence of coronary heart disease, associated manifestations and electrocardiographic findings in elderly Finns

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1 Age ad Ageig 1998; 27: , British Geriatrics Society Prevalece of coroary heart disease, associated maifestatios ad electrocardiographic fidigs i elderly Fis MERJA AUTO 1 ' 2, RAIMO ISOAHO 2, HANNU PUOUJOKI 3, PEKKA LMPPALA 4, MATTI ROMO 5, SIRKKA-LJISA KIVELA 1 'Uit of Geeral Practice, Oulu Uiversity Hospital ad Departmet of Public Health Sciece ad Geeral Practice, Uiversity of Oulu, Aapistie I, FIN Oulu, Filad 2 Departmet of Public Health ad Geeral Practice, Uiversity of Turku, Lemmikaisekatu I, FIN Turku, Filad 3 Medical School ad 4 Tampere School of Public Health/Biometry Uit Uiversity of Tampere ad Tampere Uiversity Hospital, ROB. 607, FIN-33IOI Tampere, Filad 5 Fiish Heart Associatio, Oltermaitie 8, FIN-OO62I Helsiki, Filad Address correspodece to: M. Ahto. Luusmaetie 5 as 3, FIN Lieto, Filad. Fax: (+358) merjaahto@utu.fi Abstract Objective: to study the prevalece of coroary heart disease (CHD) ad its cliical maifestatios amog Fiish elderly people i a cross-sectioal epidemiological survey i the rural district of Lieto, southwester Filad, with special emphasis o the overlap of CHD maifestatios with electrocardiogram (ECG) fidigs ad factors associated with CHD. Desig: observatioal populatio-based study. Settig: Health Cetre i Lieto, Filad, Subjects: 488 me ad 708 wome aged years. Mai outcome measures: agia pectoris (AP) ad dyspoea were recorded usig the Lodo School of Hygiee cardiovascular questioaires. Restig ECG fidigs were aalysed ad coded. Miesota codes , , or 7.1 were iterpreted as ischaemic. The medical history of cardiovascular diseases was based o medical records. Results: the prevalece of AP was 9.1 [95 cofidece iterval (CI): ] amog me ad 4.9 ( ) amog wome. The respective figures for myocardial ifarctio (MI) were 139 ( ) ad 6.5 ( ). Ischaemic ECG fidigs were commo: 32.9 ( ) of me ad 39.3 ( ) of wome had such chages, whereas oly a miority of them reported typical AP. The total prevalece of CHD, icludig AP, MI, past coroary artery by-pass operatio or agioplasty or ischaemic ECG fidigs, was 37.7 ( ) i me ad 42.0 ( ) i wome. Amog me, a higher prevalece of CHD was associated with icreasig age [odds ratio (OR) 1.81; 95 CI: ] ad a history of havig smoked i the past (OR 1.66; ), whereas amog wome it was associated with icreasig age (OR 2.02; ) ad a lower educatioal level (OR 2.30; ). Coclusio: the prevalece of CHD amog elderly people is high ad the cliical picture of the disease is variable. The ature of CHD seems to be less severe amog elderly wome compared with me. Mior ECG chages, especially i the ST ad T segmets, are commo with ageig ad should ot ecessarily be iterpreted as ischaemic. However, these fidigs combied with atypical chest pai or dyspoea i a elderly perso may idicate the possibility of CHD. Keywords: aged, agia pectoris, atypical chest pai, chest pai, coroary disease epidemiology, electrocardiography, myocardial ifarctio, prevalece, risk factors 729

2 M. Ahto et al. Itroductio The prevalece of coroary heart disease (CHD) icreases with icreasig age [1, 2]. A extesive autopsy study has show occult sigificat coroary artery disease to be preset i most elderly idividuals [3]. Half of the deaths amog the populatio aged 64 years or over i Filad are caused by cardiovascular diseases ad every third death is caused by ischaemic heart disease, maily acute myocardial ifarctio (MI) [4]. However, i may developed coutries, CHD mortality i elderly people has decreased durig the last two decades [5]. Because of the cotiuous icrease i the elderly populatio ad the high frequecy of CHD world-wide, the disability caused by the disease will be commo. The prevalece rates of CHD are usually based o cardiovascular questioaires, medical records ad electrocardiogram (ECG) chages. The problem with questioaires is that characteristic agia is ot always the predomiat presetig symptom of myocardial ischaemia i a elderly patiet, but shortess of breath, weakess, cofusio or eve sycope may occur [6]. Ischaemic ECG chages are commo i elderly idividuals ad have bee cosidered somewhat o-specific. A classificatio system for restig ECG i populatio studies has bee developed ad also tested i a elderly populatio [7]. This study is part of a research project o the epidemiology of cardiovascular ad respiratory [8] diseases i elderly people (the Lieto study). The aim of the preset study was to ivestigate the prevalece of CHD ad its maifestatios i a elderly populatio. Populatio ad methods The Lieto study This cross-sectioal survey was carried out i the semiidustriali2ed rural commuity of lieto, Filad, i The survey populatio cosisted of subjects bor i or before 1926, residig i lieto ad registered o 23 March Of 1360 residets who were ivited to participate, 77 died before they could be examied ad 1196 idividuals 488 me ad 708 wome took part i the study, givig a 93 participatio rate. The survey started i October 1990 ad lasted util the ed of December 1991 [8]. The study protocol icluded iterviews, tests ad measuremets. Persoal data, socio-ecoomic ad other backgroud data (e.g. drug use ad the history of smokig) were recorded. Emphasis was placed o physical, metal ad social fuctioal abilities as well as o tests assessig cogitive impairmet ad depressive symptoms. Cardiovascular symptoms were recorded usig the Lodo School of Hygiee cardiovascular questioaires [9]. Dyspoea was measured by Medical Research Coucil questioaires [10, 11]. Due to a iability to walk, physical disability or severe demetia, o graded dyspoea data were obtaied from 10 me ad 34 wome. Chest radiographs (posterior-aterior ad lateral views) were take ad heart size was measured [12, 13]. Twelve-lead restig ECGs were recorded (MAC 6, Marquette Electroics, Milwaukee, WI, USA). The electrocardiograms were coded by a member of the research team (H.P.) accordig to the Miesota code 1982 [9]. The participats made two visits to the health cetre, ad durig the first visit were examied by two traied urses. Previous medical records, completed questioaires ad other results from the survey examiatios were reviewed before the participats came for their secod visit, durig which a cliical examiatio by a physicia (R.I.) was carried out. Eight out of the 1196 participats (0.7) refused to be examied by the physicia after their first visit. Defiitios ad diagostic criteria Agia pec torts (AP) A perso was defied as havig AP if he/she had chest pai o effort fulfillig the Rose questioaire's criteria [9]. AP was divided ito two grades of severity accordig to the same criteria. Atypical chest pai Atypical chest pai was preset if a perso had felt discomfort or pai i the chest o effort ot fulfillig the AP criteria or at rest. I cases of severe demetia, the assessmet of chest pai was based o previous cliical documets ad proxy iterviews. MI A perso was deed as havig MI if he/she had a positive history of MI i the medical records (a summary report after discharge from a hospital or a health cetre ipatiet ward) or a major or moderate Q/QS item (Miesota code 1.1 or 1.2) o electrocardiography [14]. Dyspoea The grades of dyspoea were deed accordig to the Medical Research Coucil criteria [9], but grade 0 was assiged to those who aswered 'o' to all the dyspoea questios. Mior ECG chages These were defied as positive Miesota codes 1.3, , , or 7.1 o ECG. CHD CHD was defied as beig preset whe the perso 730

3 Prevalece of CHD i elderly people met at least oe of the followig criteria: (i) typical history of AP, (ii) previous MI, (iii) ischaemia o ECG: Miesota codes , , , or 7.1 positive [14], (iv) history of coroary by-pass surgery or (v) history of coroary agioplasty. Smokig A perso who had smoked at least oe cigarette per day (or oe large cigar per week or 28 g (1 ouce) of tobacco per moth) for as log as a year or more ad who, at the time of the iterview, had ot smoked for the previous 6 moths or more was defied to be a exsmoker [ 11 ]. A perso who had still smoked durig the last 6 moths was defied as a smoker. Statistical methods The results were aalysed by cross-tabulatio. The \ 2 test or Fisher's exact test was used i comparig the categorical variables. The 95 cofidece itervals (CI) were calculated by the Cofidece Iterval Aalysis software [15]. The associatios betwee the occurrece of CHD ad possible risk factors, sociodemographic factors ad cliical characteristics were studied with logistic regressio aalysis, the results of which were summarized usig odds ratios with 95 cofidece itervals. The fit of the model was measured usig Hosmer-Lemeshow statistics [16]. The computatio was carried out o a IBM VM/SP computer usig the SAS library [17] ad the BMDP statistical software [18]. Results The mea age of me was 72 years (SD 7 years, rage years) ad that of wome 74 years (SD 7 years, rage years). The mea age of male patiets with CHD was 74 years (SD 6 years, rage years) ad that of female patiets 76 years (SD 7 years, rage years). Of the whole study populatio, 96 of me ad 94 of wome lived at home. The remaiig 4 of me ad 6 of wome were i log-term istitutioal care, as compared with 5 of me ad 10 of wome with CHD. Subjects with AP The prevalece of AP based o Rose's questioaire was 9 i me ad 5 i wome (Table 1). The prevaleces for AP based o medical records were higher 13 amog me ad 8 amog wome. 57 (95 CI: ) of me with AP ad 54 ( ) of wome had ischaemic fidigs o ECG. Subjects with atypical chest pai Atypical chest pai was reported by 26 (95 CI: ) of me ad 28 ( ) of wome. 44 ( ) of me with atypical chest pai ad 54 ( ) of respective wome had ischaemic ECG abormalities. 65 of me ad 68 of wome did ot report ay kid of chest pai. The Ve diagram i Figure 1 shows the umbers of people with atypical chest pai, MI ad mior ECG chages. Table I. Number (ri) ad proportio () of subjects meetig differet coroary heart disease (CHD) criteria by sex Criterio Chest pai o effort (grade) 3 I or II I History of myocardial ifarctio Coroary by-pass surgery Agioplasty ECG fidigs (Miesota code) b , , ,7.1 Total c Sex Me ( = 488) CI Wome («= 708) CI Differece (P-value) CI, cofidece iterval; ECG, electrocardiogram. "Iformatio of chest pai was ot obtaied from two me. ""ECG recordig was ot obtaied from two me ad ie wome. C A subject may meet more tha oe criterio. 731

4 M. Ahto et al. Subjects with previous Ml Sixty-eight me ad 46 wome were diagosed as havig previous MI. Thus, the prevaleces were 14 (95 CI: ) for me ad 7 ( ) for wome. The prevalece of MI based purely o medical records was lower 9 of me ad 3 of wome (Table 1). The patiets with previous MI reported atypical chest pai more commoly tha typical AP (Figure 1). Subjects with dyspoea 19 (95 CI: ) of me ad 18 ( ) of wome suffered from troublesome breathlessess (grade, i or IV). Nearly half the me with moderate MEN (N=488) Agia pec tos (N=44, prev. 9) Myocardial ifarctio (N=68, prcv. 14) WOMEN (N=708) Myocardial ifarctio (N=46, prev. 7) Atypical chest pai (N=125, prev. 26) Agia pectoris (N=35, prev. 5) Mior ECG chages (N=136, prev. 28) Mior ECG chages (N=258, prev. 37) Atypical chest pai (N=195, prev. 28) Figure I. Ve diagrams showig the umber of elderly me ad wome with various maifestatios of coroary heart disease ad mior electrocardiogram (ECG) chages ad their overlap. The rectagle shows the umber of elderly persos with atypical chest pai ad its overlap by myocardial ifarctio ad mior ECG chages. 732

5 Prevalece of CHD i elderly people Table 2. Prevalece of the ischaemia-associated electrocardiography (ECG) fidigs which differed sigificatly i their occurrece by sex Sex Me Wome ( = 708) ( = 488) Miesota code ECG abormality Major Q/QS patter Total Q/QS patter ST juctio depressio of <0.5 mm Total ST juctio depressio T wave iversio of <1 mm Total T wave iversio Differece (P-value) or severe dyspoea ad slightly more tha half the respective wome had ischaemic ECG abormalities. ECG fidigs The most commo ischaemic ECG fidig was T wave iversios (Miesota codes ) amog both sexes (Table 2). A major Q/QS patter (code 1.1) was more commo i me, whereas mior ST juctio depressios (code 4.3) ad mior T wave iversios (code 5-3) were more commo i wome (Table 2). The most commo Q/QS patters were a moderate Q/ QS patter (code 1.2) amog me ad a mior Q/QS patter (code 1.3) amog wome. A moderate Q/QS patter ad T wave iversios of 1-5 mm ad less tha 1 mm (codes 5.2 ad 53) were the three most commo ischaemic fidigs amog me. ST juctio depressios of less tha 0.5 mm (code 4.3) ad T wave iversios of 1-5 mm ad less tha 1 mm were the three most commo ischaemic fidigs i wome. The prevalece of atrial fibrillatio was 9 (95 CI: ) i me ad 4 ( ) i wome. Atrial fibrillatio was more commo amog CHD patiets tha amog those without CHD: 15 ( ) of me with the disease ad 5 ( ) of me without it had atrial fibrillatio o ECG, while for wome the correspodig figures were 9 ( ) ad 1 ( ). Figure 1 illustrates how ofte the mior ECG chages occurred without a previous MI or a history of AP. wome were ex-smokers ad 12 of me ad 4 of wome were curret smokers. Hypertesio was more commo amog CHD patiets tha amog those without the disease: 35 (95 CI: ) of me with CHD ad 22 ( ) of me without had a diagosis of hypertesio i the medical records. The correspodig figures for wome were 49 ( ) ad 33 ( ). Twety-four percet (95 CI: ) of me ad 12 ( ) of wome with CHD suffered from AP, while atypical chest pai was reported by 32 ( ) of me ad 36 ( ) of wome. Subjects without CHD reported atypical chest pai less frequetly tha those with the disease preset: i this group the figures were 22 ( ) i me ad 21 ( ) i wome. I the CHD group, 37 (95 CI: ) of me ad 16 ( ) of wome had had a previous MI. The umber of udiagosed Mis i the total study populatio was low: 5 amog me ad 4 amog wome. 62 Subjects with CHD Total CHD prevalece was 38 i me ad 42 i wome (Table 1). Amog me, the prevalece was highest i those aged years, while amog wome it was highest i the oldest age group of 85 years or over (Figure 2). hi the group with CHD, 60 of me ad 6 of Figure 2. Prevalece of coroary heart disease by age for me ( ; = 488) ad wome ( ; = 708). 733 'ECG recordig was ot obtaied from two me ad ie wome.

6 M. Ahto et of. Dyspoea of grades II-IV was see i 29 (95 CI: ) of me with CHD ad 13 ( ) of me without the disease; the figures for wome were 26 ( ) ad 12 ( ) respectively. Very few CHD patiets had a diagosis of curret asthma or chroic obstructive pulmoary disease: six me (3) ad 15 wome (5) had curret asthma while 16 me (9) ad seve wome (2) had chroic obstructive pulmoary disease. Obesity (defied as a body mass idex >30kg/m 2 ) was see i 25 ( ) of me with CHD ad 17 ( ) without the disease; the figures for wome were 32 ( ) ad 33 ( ) respectively. The logistic regressio aalysis amog me showed a higher prevalece of CHD to be associated with icreasig age ad a history of havig smoked previously (Table 3). OR was low amog me who had worked i the maufacturig idustry or costructio. Amog wome, a higher prevalece of CHD was associated with icreasig age ad a lower educatioal level. Discussio The prevalece of CHD rises with icreasig age i wome. A similar tedecy occurs i me, but is less proouced i the oldest age group of me (aged 85 years ad over) tha i those aged years. Similar treds i the prevalece figures have also bee see i other populatio-based studies [1, 2]. The reaso for the lower prevalece i me is probably the higher icidece ad mortality from CHD amog middle-aged me. CHD is usually more severe i ature i me tha i wome ad a greater proportio of me have suffered MI or have typical AP. Also, the umber of female patiets who are curret or ex-smokers is low, which is oe reaso why more wome with CHD have survived loger tha me. I me aged years, the survivors of the Fiish cohorts of the Seve Coutries Study, the total prevalece of CHD was 45 [19], whereas thefigurei our study was 49 i me aged years. I the 'Mii-Filad Health Survey', the figures for CHDrelated ECG fidigs were somewhat differet from those reported here, possibly due to the differet criteria used [20]. I our study, the figures for ECG evidece of MI were higher ad those for mior ECG chages lower. The total prevalece of CHD i Iieto is higher tha elsewhere i Scadiavia [21] or i Europe [22]. Various studies from USA [2, 23], Australia [1] ad Asia [24, 25] have also reported lower prevalece figures i elderly subjects. As yet o cosesus has bee reached amog epidemiological surveys o the criteria for CHD applicable to elderly people. Ay compariso of fidigs is difficult because of the variable criteria. Some studies report the overall prevalece figures of self-reported disease rather tha usig criteria based o electrocardiography [22]. I some studies the age of those surveyed has differed from ours. Our results, however, support the coclusio that CHD morbidity is high amog the elderly populatio of Filad. To preset our ischaemic ECGfidigs, we used the same Miesota codes that were used i the Whitehall studies, which were carried out i middle-aged people [14]. Woo et ai, i their studies of a elderly Chiese populatio, used the 'Whitehall criteria' i defiig ischaemia [24], ad their ECG fidigs suggestig possible ischaemia were lower tha ours. I some studies, the oly ECG evidece of CHD has bee a pathological Q wave with a duratio of 0.04 secod or loger [23] or a major Q wave [25]. I the Cardiovascular Health study, the diagosis of CHD was partly based o 'cardiac ijury' ad the system of scorig it with age [2]. The Miesota codes are useful i populatio studies [7], but attetio must be give to the effect of age o the ECG, (especially i populatios with high prevalece of CHD [26]), ST ad T wave chages (particularly the digitalis effect) ad right ad left vetricular hypertrophy patters. The use of digitalis is commo i elderly Fis, ad this may have iduced part of the ST depressio chages i our study: 26 of me ad 33 of wome with CHD were usig digitalis. I additio, hypertesio was also commo i the CHD patiets. However, the Q/S patters, the ST-T patters, icludig T wave flatteig as well as iversios, ad the voltage chages of left vetricular hypertrophy i elderly subjects caot be disregarded or take merely as a sig of ageig [27]. Recet studies have show the progostic value of icreased left vetricular mass for CHD [28] ad vice versa: repeated ischaemia i dogs may iduce left vetricular hypertrophy [29]. Some researchers have accepted atrial fibrillatio as oe of the diagostic criteria for CHD but, despite its associatio with CHD ad old age, valvular diseases, cogestive heart failure, hypertesio ad diabetes mellitus are idepedet risk factors for the developmet of atrial fibrillatio [30]. Furthermore, hyperthyroidism, alcohol itoxicatio ad the use of choliergic drugs are also risk factors [31]. Although we did ot accept atrial fibrillatio as a criterio for CHD, the associatio betwee atrialfibrillatioad CHD is see i our study. The preset prevalece of AP amog both me ad wome is lower tha i previous studies i Filad [19, 20] ad i the USA [2], with the exceptio of the Hawaii study [25]. Daish prevalece figures for AP amog 70-year-old people [32] are similar to those obtaied i our populatio aged 64 years ad over. AP questioaires are commoly used as tools i epidemiological studies o the prevalece of ischaemic heart disease. However, with icreasig age the perceptio of pai durig myocardial ischaemic episodes becomes muted, ad this relatioship remais sigificat eve 734

7 Prevale a f CHDi elderl]f peop Table 3. Number of subjects ad prevalece () of coroary heart disease by sex, age, history of smokig, previous occupatio ad educatio, ad logistic regressio aalysis with age, social status, occupatio, smokig, educatio, marital status ad body mass idex as related factors Age (years) History of smokig 3 No-smoker Ex-smoker Smoker Previous occupatio Service sector/admiistratio/teachig Maufacturig idustry/costructio work Agriculture Work i family Educatio More tha basic" Basic" Less tha basic Hosmer- Lemeshow Me ( = 488) Cases/subgroup 106/322 78/166 52/ /268 22/72 32/58 78/262 74/168 10/35 156/405 18/ P = OR (95 CD Ref ( ) Ref. 1.66( ) 1.25( ) Ref ( ) 0.62( ) Wome ( = 708) Cases/subgroup 143/ / /638 18/42 11/24 66/155 61/ /287 45/99 15/46 236/590 46/ OR (95 CD Ref. 2.02( ) - i i i i 33 Ref ( ) P = : OR, odds ratio; CI, cofidece iterval; Ref, referece group. "Icomplete data o four wome. b Combled i the logistic regressio aalysis. i

8 M. Ahto et al. whe the presece of medicatio ad the severity of disease are cotrolled for [33]- I some studies, the presece of AP has bee cofirmed by a physicia's iterview rather tha stadardized questioaires [2]. There are possible biases whe the physicia's iterview is used for the diagosis of AP or eve whe stadardized questioaires are used i epidemiological studies of AP [34]. The Rose questioaire has tured out to be highly specific ad fairly sesitive whe compared with the physicia's diagosis of AP amog me [35], but its validity amog wome remais ucertai [36]. At 26 for me ad 28 for wome, our prevalece figures for atypical chest pai are fairly high. This may be because we strictly observed the istructios of the Rose questioaire whe iquirig about the presece of AP. However, early half of me ad slightly more tha half of wome with atypical chest pai had ischaemic ECG fidigs. May people reported takig itroglycerie ad cotiuig walkig without rest i spite of chest pai. Chest pai i wome with CHD seemed to be more ofte atypical. The possibility of microvascular agia as a cause of chest pai with agiographically ormal coroary arteries [37] should be remembered whe evaluatig atypical chest pai i elderly people. Me showed a associatio betwee CHD ad havig smoked i the past. No such associatio was foud betwee CHD ad curret smokig. The explaatio might be that subjects had give up smokig whe symptoms of CHD arose, hi a cohort of Japaese-America me aged 65 years ad over durig a 12-year follow-up period, the CHD icidece rates icreased progressively i idividuals classified at baselie as ever, former ad curret smokers, respectively [38]. Curret cigarette smokers, especially me, have a icreased risk of CHD death compared with o-smokers, ex-smokers or smokers of pipes ad cigars [39] The excess risk of death declied withi 1-5 years of cessatio of smokig. Due to the crosssectioal desig of our study, smokig as a risk factor for CHD has bee uderestimated. We foud a relatioship betwee a low level of basic educatio ad CHD amog wome. This result is cosistet with a recet Fiish fidig: lower levels of educatio, occupatio ad icome are associated with a icreased cardiovascular risk i middle-aged me ad wome [40]. Me who have bee workig i the maufacturig idustry ad costructio work have a low risk of CHD. This may be due to some sort of selectio i the past: healthy me have probably chose physically demadig work. Aother explaatio might be some protective effect of physical activity o CHD [41]. I coclusio, the prevalece of CHD i elderly Fis is high, with mior ECG chages (especially i the ST ad T segmets) frequet i this populatio. These fidigs are commo ot oly i CHD but also with ageig, i left vetricular hypertrophy ad i digoxi users. Previous Ml was a commo fidig i our study populatio. The prevalece of typical AP is fairly low, idicatig that the cliical picture of CHD i elderly people may vary from severe symptoms to o symptoms. However, the proportio of people havig some form of discomfort or pai i the chest o effort due to CHD is larger tha the prevalece of typical AP derived from the Rose questioaire. Atypical chest pai with mior ECG chages is commo, especially amog wome. Key poits Atypical chest pai with ischaemic electrocardiographic chages is commo i elderly people, especially amog wome. Mior electrocardiographic chages especially i the ST ad T segmets are commo with ageig but these fidigs, combied with atypical chest pai or dyspoea, may idicate the possibility of coroary heart disease. Coroary heart disease seems to be less severe i elderly wome tha me. Ackowledgemets This research was supported by grats from the Academy of Filad, the Yrjo Jahsso Foudatio, the Uulo Arhio Foudatio, the Ida Moti Foudatio ad the Heart District of Varsiais-Suomi. Refereces 1. Simos LA, Friedlader Y, McCallum J et al. The Dubbo Study of the health of the elderly: correlates of coroary heart disease at study etry. J Am Geriatr Soc 1991; 39: Bild D, Fitzpatrick A, Fried L et al. Age-related treds i cardiovascular morbidity ad physical fuctioig i the elderly: the Cardiovascular Health Study. J Am Geriatr Soc 1993; 41: Elveback L, Lie JT. Cotiued high icidece of coroary artery disease at autopsy i Olmsted Couty, Miesota, 1950 to Circulatio 1984; 70: Statistics Filad. Causes of death Series Health 1993; 9: WHO Study Group. Epidemiology ad prevetio of cardiovascular diseases i elderly people. WHO Techical Report Series No 853. Geeva: World Health Orgaisatio, 1995; Mcltosh HD. Presetatio ad evaluatio of ischemic heart disease. I: Chesler E, ed. Cliical cardiology i the elderly. Armok, NY: Futura, 1994; Blackbur H, Keys A, Simoso E, Rautahariu PM, Pusar S. The electrocardiogram i populatio studies. A classificatio system. Circulatio I960; 21:

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10 < Steve Bloch.