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CLINICAL INVESTIGATIONS

Atrial Fibrillation Developing in the Acute Phase of Myocardial Infarction· Prognostic Implications N. Cristal, M.D.; I. Peterburg, M.D.; and]. Szwarcberg (Shahar), M.D. Atrial fibrillation was observed in 39 (11 percent) of 350 instances of acute myocardial infarction. The mortality among these .-tients was 41 percent (16/39). Atrial fibrillation was more common in patients with undetermined infarctions aDd In older people. As opposed to death rates close to 50 percent among patients with anterior, combined, and undetermined infarctions, the presence of atrial fibrillation did not dect the mortality among patients with inferior infarctioDS (10 percent, 1110). Ventricular rates higher than 120 beats per minute and

I t is a common belief that atrial fibrillation is the

arrhythmia associated with the highest mortalityl-S during the early phase of acute myocardial infarction. Nevertheless, it is yet unsettled whether For editorial comment, see pag~ 3

abial fibrillation per se is the cause of the high mortality or is just an electrocardiographic manifestation of the mechanism responsible for the grave . prognosis. This study presents new data on the prognostic significance of atrial fibrillation in the setting of acute myocardial infarction. MATERIALS AND METHODS

This report is based pn 350 instances of acute myocardial infarction occurring in 318 patients admitted consecutively to the coronary care unit over a period of 20 months. Of the 318 patients (mean age, 60 years), 242 were men, and 76 were women. This population was reviewed in order to evaluate the incidence and mortality associated with supraventricular arrhythmias. The results of that study were previously reported by us.6 A total of 39 imtances of atrial fibrillation (including three cases of atrial flutter) developing during the acute phase of myocardial infarction fonn the basis of the present study. We decided to consider atrial fibrillation and atrial flutter together, since in our experience the differential diagnosis between flutter and fibrillation in acute myocardial ·From the Coronary Care Service, the Soroka Medical Center, Beersheba, Israel. Manuscript received September 29; revision accepted January 15. Reprint requests: Dr. Cristal, Beer Sheva Hospital, Beer Sheva, Israel

8 CRISTAL, PETERBURG, SZWARCBERG

duration of the arrhythmia longer than six hours were not associated with increased mortality. Hemodynamic fallure was present In almost all of the cases and preceded the arrhythmia in most of them. It is concluded that different mechanisms are responsible for the production of atrial fibrillation in the setting of acute myocardial illfarctioo, and the prognosis of the patient is related to the mechanism of production and not to the arrhythmia itself.

infarction Is not always obvious, and careful examination of a standard lead or of an intra-atrial recording frequently showed the presence of regular, fast F waves with irregular ventricular response (fibrilloflutter). Flutter was diagnosed when the abial rate was over 260 contractions per minute. Henceforth, this group will be referred to as having atrial fibrillation. Patients known to have atrial fibrillation before admission were excluded from analysis. Acute myocardial infarction was diagnosed by the occurrence of at least two out of the following three criteria: (1) typical clinical symptoms; ( 2) Q wave developing in consecutive electrocardiograms; and (3) a diagnostic rise in the serum enzyme levels of serum glutamic oxaloacetic transaminase and creatine phosphokinase. Four positions of infarction were classified: (1) anterior, when Q waves developed in leads 1 and aVL or in precordial leads VI through V6, or both; (2) "inferior," when the Q wave was present in leads 2, 3, and a VF, or in the presence of a pattern of true posterior infarction; (3) combined, referring to involvement of inferior plus anterior, lateral, or septal wall; and (4) undetermined, in cases with left bundle-branch block or when the diagnosis was entertained by clinical symptoms together with a rise in serum enzyme levels. Most patients in the latter category had sustained a previous myocardial infarction, and although dynamic ST-T changes were present, new Q waves did not develop. . In every patient, the coronary prognostic index of Norris et al7 was detennined upon admission. Three degrees of heart failure were defined: (1) mild, the presence of radiologic evidence of pulmonary venous congestion without any clinical signs; (2) moderate, the presence of clinical evidence of heart failure (elevated jugular venous pressure, persistent basal rales, third and fourth heart sounds) and radiologic findings (cardiomegaly, differential blood How to the upper lobes, interstitial edema, and Kerley's B lines); and (3) pulmonary edema.

CHEST, 70: 1, JULY, 1976

cent. This finding contrasts with the overrepresentation of women among patients with atrial fibrillation reported by Helmers et al. 1

Hypotension was defined as the presence of a systolic blood pressure below 90 mm Hg without other features of the shock syndrome. Cardiogenic shock was considered to be present when there was a systolic blood pressure less than 80 mm Hg, cold and clammy extremities, cyanosis, and oliguria (less than 20 mm/hour), often with mental apathy and restlessness. The median arrival time, from the onset of symptoms until admission to the coronary care unit, was .a hours. 8 The patients remained in the coronary care unit for a period of 48 to 72 hours, or until free of complications for at least 24 hours. The electrocardiographic tracings were displayed on a bedside monitor and at the nurses' station; each arrhythmia detected was recorded with the aid of a 45-second memory loop. A therapeutic schedule similar to that reported by DeSanctis et al9 was followed. The statistical significance of the data was analyzed by the chi-square method.

Age

Atrial fibrillation occurred more commonly in older patients (mean age, 67 years; 47 percent or 18 of 38 older than 70 years), which is in accordance with the findings of Helmers et al. l No relation was found between age and prognosis. Location of Infarction

Atrial fibrillation developed in 22 percent (13) of the 60 patients with infarction of undetennined location (Table 1), an incidence significantly higher than the incidence of the arrhythmia among infarctions in other locations (P < 0.025), a finding previously stressed. 1 As opposed to death rates close to 50 percent among patients with anterior, combined, and undetennined infarctions, the presence of atrial fibrillation did not affect the mortality among patients with inferior infarction (10 percent or 1/10, as opposed to 9 percent or 7/81 in the remainder).

REsULTS

Incilknce Atrial fibrillation was observed in 39 instances (38 patients), making an incidence of 11 percent. This incidence corresponds to that reported in previous studies. 1-5.10-14 Mortality

Sixteen (41 percent) of the 39 instances caused death during hospitalization, as compared to 13 percent (41/311) of the remainder (P < 0.01). This increased mortality associated with atrial fibrillation in the setting of acute myocardial infarction is similar to those death rates reported by Klass and Haywood4 (42 percent), by Helmers et all (38 percent), by Hurwitz and Eliot2 (38 percent), and by Stannard and Sloman5 (41 percent). In contrast, other previous reports 10- 12 ,14 failed to demonstrate an increased mortality.

Applying the prognostic index of Norris et al,7 which allows an objective assessment of the patient's clinical status and in which the score calculated reflects the severity of the disease on admission, it is evident (Table 2) that the worse the clinical status, the greater was the incidence of atrial fibrillation and the mortality associated with it. A similar finding was reported by Stock and Goble. 14

Sex

Ventricular Rate

Seven women out of the 76 in the whole series developed atrial fibrillation, an incidence of 9 per-

A high ventricular rate (over 120 beats per minute) was found to be associated with a lower, al-

Prognostic Index

Table I-Morlali'y in Aeute Myoeardialln/aretion Aeeordin«

'0 Site o/ln/aretion

Site of Infarction Anterior

Inferior

Combined

Undetermined

153

91

46

60

350

Mortality, percent

18

9

17

22

16

Atrial fibrillation No. of patients Incidence, percent

10 6

10 11

6 13

13 22

39 11

Deaths with atrial fibrillation No. Mortality, percent

5 50

1 10

50

7 54

16 41

Mortality of remainder, percent

16

9

12

17

13

Atrial fibrillation developing in the acute phase of myocardial infarction. Prognostic implications.

Atrial fibrillation was observed in 39 (11 percent) of 350 instances of acute myocardial infarction. The mortality among these patients was 41 percent...
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