Acute Myocardial Infarction Clinical Features of 113 Patients

Ventricular Tachycardia in Acute Myocardial Infarction Clinical Features of 113 Patients

A. Beryl Farfel, MD, Herman H. Ricketts, MD, and L. Julian Haywood, MD Los Angeles, California

This study was undertaken to evaluate the clinical significance of until discharge. Direct write-out elec- ventricular tachycardia as a complication of acute myocardial infarc- trocardiographs were available but tion in a large public hospital. An analysis of the clinical, electro- memory loops were out. All arrhythmia records were obtained by manual cardiographic, therapeutic, and prognostic implications of this large activation of the monitor system by patient group is presented and several unique features emphasized. trained nursing or physician personnel. The records of 113 patients with ventricular tachycardia were reviewed. Age, sex, onset of symptoms, onset of Ventricular tachycardia is an impor- Methods ventricular tachycardia, type and char- tant complication of acute myocardial All patients admitted to the Coro- acteristics of ventricular tachycardia, infarction, and prior to continuous nary Care Unit of the Los Angeles- therapy, outcome, location of infarct, monitoring, the incidence of this County-University of Southern Cali- associated arrhythmias, and compli- arrhythmia was estimated as one to fornia Medical Center between Octo- cations were catalogued for each pa- two percent.1-6 This arrhythmia has ber 1966 and October 1968, formed tient. been recognized with much greater the basis of the study. Of 416 total frequency in coronary care units and patients, 330 (79.3 percent) were con- Definitions its incidence has been reported as ten sidered to have acute myocardial in- Ventricular tachycardia (VT) is de- to thirty percent.7-11 In the early farction. The average stay in the unit fined as three or more depolarizations phases of myocardial infarction, even was 7.8 days. in sequence from an ectopic ventric- higher incidences have been Criteria for the diagnosis of myo- ular focus exceeding 60 per min- noted.1 2,1 3 During the last decade, cardial infarction were at least two of ute.14 Three types may be distin- the introduction of closed chest mas- the following: (1) pathological Q guished, namely, extrasystolic, para- sage, electrical reversion, continuous waves associated with S-T segment systolic, and idioventricular.15 Extra- electrocardiographic monitoring, and elevation and subsequent evolutionary systolic ventricular tachycardia begins newer anti-arrhythmic drugs have changes of the S-T segment and T with an extrasystole and can be viewed greatly altered the clinical course and wave; (2) elevation of the serum glu- as a series of three or more ventricular prognosis of ventricular tachycardia. tamic oxaloacetic acid transaminase extrasystoles. Ventricular extrasystoles Much of the reduction in mortality (SGOT), creatinine phosphokinase are characterized by a fixed-coupling demonstrated in acute myocardial in- (CPK), and lactic acid dehydrogenase interval between the preceding sinus farction, treated in coronary care (LDH); and (3) a typical clinical his- initiated ventricular (QRS) complex units, can be attributed to the preven- tory. In the presence of left bundle and the ectopic QRS complex. In this tion, prompt recognition, and treat- branch block, a history compatible form of ventricular tachycardia, the ment of this arrhythmia.1 1 with myocardial infarction and en- inter-ectopic intervals between parox- zymatic changes were required as ade- ysms are not in multiples of the quate evidence. The onset of infarc- ectopic cycle length, indicating the tion was timed with the occurrence of absence of a parasystolic mechanism precordial chest pain or increased (Figure 1). severity and frequency of chest pain in Parasystolic ventricular tachycardia From the University of Southern California patients with pre-existing angina. is characterized by a variable coupling Medical Center, Los Angeles, California. Re- quests for reprints should be addressed to Continuous oscillographic monitor- interval and the inter-ectopic intervals Dr. L. Julian Haywood, Box 305, 1200 North State Street, Los Angeles, Calif ing was initiated immediately on ad- between paroxysms are in simple mul- 90033. mission to the unit and continued tiples of the ectopic cycle lengths

JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 2, 1977 109 (Figure 2). The phenomenon of en- detect arrhythmias. (The incidence of minute). Second or third degree A-V trance block or "protection" is mani- other arrhythmias was comparable to block occurred in 17 patients, paced fested. units having memory write-outs). The rhythms in four, atrial fibrillation in Idioventricular tachycardia is an es- high incidence of occurrence may have seven, auricular flutter in two, and cape rhythm which is enhanced - an been influenced by some bias in pa- nodal rhythm in three. accelerated idioventricular rhythm' 6 tient selection for a small unit, in that Single episodes of ventricular tachy- (Figure 3). there was a tendency to select patients cardia occurred in 23 patients (20 Attempts were made to classify who were unstable as compared to percent) whereas recurrences were each episode of ventricular ectopic others. The patient population other- documented in 90 patients (80 per- rhythm into one of the above three wise was self defining. Ninety patients cent). types. (80 percent) experienced recurrent Congestive heart failure was diag- episodes of ventricular tachycardia. nosed if there was x-ray evidence of Therapy pulmonary venous engorgement or Lidocaine was successfully used as pulmonary edema, or clinical evidence Age and Sex the primary therapy in 75 patients in a of central venous pressure elevation. The patients ranged in age from 34 dosage range of 1 to 4 mg/min follow- Shock was considered to be present if to 86. The majority of patients were in ing a bolus of 25 to 100 mg depending there was persistent hypotension the sixth (31 ) and seventh (40) de- upon the frequency and duration of (systolic blood pressure less than 80 cades. Twenty-three patients were the ventricular tachycardia episodes. mm Hg), associated with oliguria, (less under the age of 50, and 19 patients In resistant cases, procainamide was than 20 cc urine output per hour), were over 70 years of age. Eighty-nine added to lidocaine either intravenously changes in sensorium, and evidence of were male and 24 were female. or orally, and in a few instances was peripheral vascular constriction, such used alone. An intravenous mixture of as cold, moist extremities. equal parts of lidocaine and procain- Results amide frequently worked when there Characteristics of Ventricular Tachy- was not a prompt response to lido- Onset of Symptoms cardia caine. Intravenous atropine (0.5 to 1 In those patients in whom the time The mode of onset of each episode mg) was the initial therapy in 13 of onset of infarction could reasonably of ventricular tachycardia was ana- patients, while quinidine orally was be estimated, there was no predilec- lyzed. All cases could not be classified used in four patients, usually as an tion for any particular eight-hour according to the criteria given. Seventy ancillary antiarrhythmic agent. period of the day. Similarly, the times patients had characteristics of extra- Thirty-three patients required elec- of onset of ventricular tachycardia systolic ventricular tachycardia, five of trical reversion. Potassium was used were evenly distributed throughout parasystolic ventricular tachycardia specifically to treat the arrhythmia in the 24-hour period. Most patients were and 14 of idioventricular tachycardia; two patients. Rarely used were admitted to the monitoring unit 24 episodes could not be clearly classi- diphenylhydantoin, magnesium sul- within eight hours after the onset of fied. Catheter pacemaker-induced or phate, bretylium tasylate, and pro- symptoms. Some patients were ad- related ventricular tachycardia was pranolol. In the presence of shock or mitted to the unit after an initial stay noted in five patients. In each of these acidosis, vasopressors and sodium bi- on another ward, either due to lack of five patients, the ventricular arrhyth- carbonate were also employed. Pace- space in the coronary care unit or to mia developed after catheter place- maker catheters were used as an ad- late recognition of the acute myo- ment, and in two disappeared after junctive mode of therapy in nine cardial infarction state. Ninety-three catheter repositioning. patients with recurrent ventricular patients had their initial documented The rate of ventricular tachycardia tachycardia. episodes of ventricular tachycardia exceeded 120 in 66 patients, was Sixteen patients reverted from the within 96 hours of the onset of between 100 and 120 in 17 patients, initial episode of ventricular tachy- symptoms. The highest incidence was and in 21 patients was less than 100. cardia spontaneously, and were not on the first day and declined there- Absolute regularity of rate was noted previously receiving therapy. Sixty pa- after. Fifty-seven percent occurred in one third of the patients. tients (53 percent) were receiving anti- within the first 48 hours. Ventricular ectopic beats were re- arrhythmic drugs at the time of onset corded in 105 patients (93 percent) of ventricular tachycardia (lidocaine, Incidence before the onset of ventricular tachy- procainamide, quinidine) usually for During this period, 416 patients cardia. Only six patients (5.3 percent) control of ventricular ectopic beats were admitted to the unit, 330 had developed ventricular tachycardia and 53 patients (47 percent) were not acute myocardial infarction (79.3 per- without previously documented ven- on antiarrhythmic drugs. A total of 53 cent), and 1 13 (34.2 percent of 330) tricular ectopic beats. Two patients had patients received procainamide. m a n ifested ventricular tachycardia ventricular tachycardia when first during the course of their illness. The monitored. high incidence of detection of ventric- The antecedent rhythm was docu- Results of Therapy ular tachycardia detection is ex- mented as sinus in 78 patients. Of The initial or subsequent episodes plained by the well-trained nursing these, 21 had sinus bradycardia (less of ventricular tachycardia were suc- staff and a physical arrangement that than 60 per minute) and 20 sinus cessfully controlled in 109 of 1 13 put the nurse in optimal position to tachycardia (greater than 100 per patients, with spontaneous remission

110 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 2, 1977 in 16 patients. Seventy-one patients were ultimately discharged from the hospital. Thirty-eight patients whose + l' 1 1 1 T.. , 1 li 1 ventricular tachycardia was success- !I .I. 11 11111 fully controlled ultimately expired 1JiM.T I 9iilil111 Aittl-illX during the hospital course. As indicated in the next section there was a IM~~~~~~~i strong association between the presence of congestive heart failure (CHF) and shock and mortality, des- It1 A111 pite control of the ventricular ectopic . RWM.!- .14' lE llilullllllllllllllllllllllllt AI lmllllllllll|- rhythm. Four patients had ventricular ----|------t tachycardia which was resistant to pharmacological therapy and all died, despite treatment with multiple drugs, IR11~~~~~~~~~~~~~~~~~~~~~~~~~~~I electric countershock, and attempted resuscitation. Three of these patients llI- 77lHl'Figure1.Ell-UiiUMfl5ili!lEiiiiiil!lll-l-::TllTA ypica examlelofHextrasystolclllvenl,ll.triclar tachyardi.' wi'!!th fixed had overt evidence of congestive fail- shown;exit-bloc.nlllll.llllullll.ltlluldllmTlilu!!!lllll!llillillmllllllmllli..l;,31.l.4umably terminat esthe episode .l;,l; 1-... coupingFigure 1.andAretrogradellA-Vtypical examplconductionof extrasystolicbegilnningventriclarith.the seconHdtachycardia.ectoic with.fixecomlexis-r ure and/or shock, one had persistent coulig nd etogadeA- cndutin eginig ithth scon etoic omleAi ventricular tachycardia as the major shown; exit blockpresumably terminates the episode. clinical complication.

Congestive Heart Failure and Shock Clinical findings consistent with congestive heart failure and/or shock were present in 73 patients (64.4 percent) at the onset of ventricular tachycardia. These findings persisted after reversion of the arrhythmia in 51 Deaths apy, and in only one instance was the patients. Clinical signs of congestive Forty-two of the 1 13 patients direct cause of death. In our patient occurred fre- heart failure or shock disappeared with studied (37 percent) died during hos- group, initial episodes quently during the first four control of the arrhythmia in 22 pa- pitalization (Table 1). Shock and/or days after onset of acute myocardial infarction tients. Ventricular tachycardia oc- congestive heart failure were present in curred in the absence of congestive 40 of these patients (95 percent). and late onset was associated with a heart failure and shock in 40 patients Second or third degree A-V block was very high mortality. Although un- (35 percent). present in 15 patients (36 percent). documented episodes of ventricular Of the patients persisting in conges- Three (7 percent) had left bundle tachycardia may have occurred while tive heart failure or shock after the branch block and seven (16.6 percent) patients were hospitalized or prior to control of ventricular tachycardia, had right bundle branch block. As admission, the significance of the re- only 13 of 51 patients were ultimately Table 2 demonstrates, late onset of ported observations would not be discharged from the hospital (25 per- ventricular tachycardia in the hospital diminished. cent). Of the group without congestive course (after 96 hours) was associated In our series, 60 patients (53 per- heart failure or shock two patients with a high mortality rate. cent) were noted to have the first ultimately died (5 percent). episode of ventricular tachycardia while receiving therapy directed at the control of documented premature ventricular beats. Dhurandhar, MacMillan, and Brown noted eight episodes of Discussion ventricular fibrillation in patients who Infarct Location The importance of treating ventric- were receiving antiarrhythmic drugs.1 9 Features of this series related to ular tachycardia complicating acute While it is clearly a desirable goal to infarct location are given in Table 1. myocardial infarction has been empha- prevent tachycardia, our experience While the incidence in inferior- sized and recent reports discuss the raises questions regarding the possi- posterior infarcts was equal to that in role of prophylactic therapy in the bility of achieving this with available anterior infarction, the mortality rate pr eve n t ion of ventricular tachy- drugs in all patients, and important was three times greater in patients cardia.17'18 This study documented side effects from the drugs themselves with anterior infarction. The slower ventricular tachycardia as a common must be considered in this context. ventricular tachycardia rates were serious complication of acute myo- The true efficacy of prophylactic ther- more common in the inferior infarct cardial infarction, which was adequate- apy can only be documented in care- patients. ly managed by presently available ther- fully observed patients and the pro-

JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 2, 1977 111 that parasystolic ventricular tachy- ...... cardia may at times appear as extrasystolic ventricular tachycardia.22 ,2 3 .1..1 [ i'l 1--1'-'] [-T-I ].-i.:'l l..~.Z- :T:::t.l':.7 77"l-'L'+- .. ...-: l-| t S t l "l Great difficulty was encountered in our series in separating idioventricular |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...... I..l:l.. U.'I...... I.-l....f'.ll...... 'l....ll'L'X from parasystolic ventricular tachy- wr~~~~~~~~k- Wv -w-vI.;l. l. -.-i v : vvv cardia. Parasystolic ventricular tachycardia was diagnosed when an inde- pendent and protected focus was Figure 2. Features of parasystole are shown: non-fixed coupling, fusion beats, common interectopic interval with protection. In the top strip, two ectopic complexes occur at demonstrated, associated with varying double the rate shown in the rest of the tracing. coupling intervals, and a common de- nominator for interectopic intervals. Our classification of various types of ventricular tachycardia was based on .1-tft E .W.1,,W,, -8- ~~X--W- 4- m -w-t:-. l-.we .t' .41: t-4..-...... the initial episode and subsequent episodes were not always clearly of the '*=:'*L:~~~~~~~~~~~~~~~~~~~~~~~~~~~ .1 same type as the initial episode. Classi- fication by initial type appeared to I.g.t....t ..lF- .l - . l .'tl. T ...l.. -.l.J.. F.- u <>lTiF4-. Iz l.tt'...1...-....'.l'''... I..:f:..t.:u-:.4::s..-t:-.t-u.fl W-2t...1.:.t:::|..:|..n..:e::tJ-: .:i:..: ...::t have prognostic significance.24 In this study, there was a considerably lower | Figure 3. Idioventricular tachycardia beginning as an escape after marked sinus slowing | mortality associated with idioven- or arrest isIJshoV'Vwn.I tricular and parasystolic types as opposed to the extrasystolic variety. The division of ventricular tachycardia into those with slow and rapid rates appears to have more practical significance. Ventricular tachycardia with rates over 100 was associated with a mortality of 42 percent (35 of 83 patients). Ventricular tachycardia with rates less than 100, regardless of type, was associated with a lower mortality (19 percent). phylactic dosages individually ad- The mortality in this group of In our view high dosage, suppressive justed.1 7 patients with acute myocardial infarc- drug therapy is not always necessary Prophylactic therapy at the onset tion complicated by ventricular tachy- or prudent in the management of of ectopic ventricular beats may in- cardia was 37 percent. Ventricular ventricular tachycardia of the slow deed decrease the incidence of rapid tachycardia as such was the cause of variety. When idioventricular tachy- ventricular tachycardia. As noted in death in only one of 42 fatal cases. cardia begins during the slow phase of this study, only six of 111 patients The remaining deaths were associated sinus arrhythmia, atropine given IV developed ventricular tachycardia with persistent cardiogenic shock and (0.5 to 2.0 mg) will often increase the without preceding ventricular ectopics. failure. Dalle, in reviewing a series of sinus rate and abolish the ectopic The treatment of ventricular ectopic ventricular tachycardia in acute myo- rhythm. Rarely does paradoxical slow- beats was based on the criteria pro- cardial infarction (53 cases) noted an ing occur. If this fails, or if the sinus posed by Lowne.20 Lidocaine intra- overall mortality of 45 percent and a rate is greater than 60, lidocaine as a venously augmented by IV or oral mortality of 80 percent when ventric- bolus (25 to 100 mg) followed by a procainamide was used in most pa- ular tachycardia began after the drip of 1 to 2 mg per minute usually tients. Blood levels were not available second day.21 Late onset ventricular su c c essfully controls the ectopic as a guide to adequacy of therapy at tachycardia in our group was also rhythm. The importance of avoiding the time of this study. Recent studies associated with poor prognosis and high doses of lidocaine in the setting show that procainamide is most effec- this group was characterized by exten- of congestive failure, shock, or liver tive when given at three to four-hour sion of myocardial infarction or pro- disease should be emphasized.25 Al- intervals.1 7 The impracticality of a gressive pump failure. When the initial though, there is a possibility that three-hour schedule is apparent and a episode occurred after the fourth day, lidocaine in high doses may depress more efficient longer acting drug is there was a 75 percent mortality normal sinus impulse formation with certainly needed. (Table 2). resulting slowing of the rate, facili- Despite favorable reports, the pres- Attempts to classify ventricular tating ectopic pacemaker activity, this ent status of prophylactic therapy tachycardia are fraught with difficulty. was not observed in this study. If with available drugs is still unclear, and Using Schamroth's classificationl 5 the atropine or low doses of lidocaine fail one must question whether the desired overwhelming majority of our patients to control the ectopic rhythm, pacing therapeutic effects can be achieved exhibited an extrasystolic type of ven- or high doses of antiarrhythmic drugs without a significant incidence of tricular tachycardia. Scherf and may be used, but may be more hazard- serious side effects. Castellanos, et al, have pointed out ous than careful observation in the

112 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 2, 1977 absence of heart failure. The primary reason for treatment of ventricular Table 1. Infarct Location and Type of Ventricular Tachycardia tachycardia particularly the fast variety is to prevent ventricular fibrillation and cardiac arrest. Ventricular tachy- Total Fatalities Extrasystolic Parasystolic Idioventricular cardia is also treated in an effort to improve cardiac hemodynamics. Treat- ment of rapid ventricular tachycardia Anterior 54 27 (50%) 39 1 3 is always indicated, and lidocaine and procainamide, singly or in combina- Inferior-posterior 47 9 (19%) 27 4 1 0 tion, are usually efficacious. Combined 3 3 (100%) Most episodes of "slow" ventricular tachycardia in our study were transi- Unclassified 9 3 4 1 tory (treated or untreated), and were not noted to lead to ventricular fibril- Totals 113 42 70 (34) 5 (1) 14 (1) lation. In some patients, however, the escape rate was variable and episodes of rapid ventricular tachycardia occurred. Lidocaine in this setting was usually effective. We have seen rare Table 2. Mortality Associated with bursts of such activity, however, with- Ventricular Tachycardia out recurrence and without apparent prognostic significance, even when no Onset of Ventricular Tachycardia Mortality therapy was given. Since slow ventricular tachycardia may not significantly alter hemodynamics because of the 0-48 hours 64 16 (25%) similarity between the slightly faster ventricular ectopic rate and the pre- 48-96 hours 29 11 (37%) ceding sinus rate, vigorous therapy to prevent the arrhythmia may not result 96 hours 20 15 (75%) in a significant improvement in cardiac hemodynamics. Ventricular pacing in such patients allows the exchange of a slow ectopic focus for a more rapid one. This may be helpful in the management of the patient in congestive heart failure. However, one may also have a pacemaker in place, since the direct current shock in this series in increase the propensity for mechani- bradyarrhythmia or A-V block often situations that were resistant to phar- cally and/or electrically induced ar- precludes the use of antiarrhythmic macological therapy or too urgent for rhythmias with the catheter pace- drugs with rate depressant effects. The continued trial of drugs. The failure to maker, itself, within the heart.26 In possibility, however, of occurrence of prevent ventricular tachycardia in this study, five patients developed a potentially life-threatening arrhyth- some cases treated with large doses of ventricular tachycardia after a pacing mia during ventricular pacemaking antiarrhythmic drugs for preceding catheter was inserted and there was should be considered as previously ventricular ectopic beats has been one patient death. (Cause and effect noted. In our experience ventricular demonstrated and the continued im- could not always be verified). Figure 4 tachyarrhythmias associated with an mergent life-saving use of DC shock shows ventricular tachycardia asso- artificial pacemaker have been con- will remain a part of CCU management ciated with a malfunctioning trans- trolled either by (1) lidocaine infusion of acute myocardial infarction until venous pacemaker. Replacing the ex- while pacing; (2) turning off the pace- more effective therapy is available. ternal pacemaker unit abolished the maker, if the ventricular tachycardia is Antiarrhythmic suppressive therapy arrhythmia. electrically stimulated; or (3) removing with drugs may have adverse effects. A-V block, second or third degree, or repositioning the pacemaker, if the Cardiac function may have been de- preceded the onset of ventricular arrhythmia is mechanically induced. pressed in those patients whose ven- tachycardia in 17 cases (15 percent). Cardioversion can be life-saving in tricular tachycardias were apparently Electrical instability in the presence of the treatment of ventricular tachy- well controlled by lidocaine and/or bradyarrhythmias and the propensity cardia but the object of coronary care procainamide. Aggravation of conges- for associated ectopic lower impulse unit management is to eliminate the tive failure or shock due to the toxic formation is well recognized.20 Forty necessity for emergency therapy. In effects of antiarrhythmic drugs on the percent of the patients in this group our unit, control of ventricular ectopic damaged myocardium certainly had a bradyarrhythmia or unstable beats has usually been accomplished o ccurs.2 7 Effective antiarrhythmic rhythm immediately preceding the on- satisfactorily with antiarrhythmic drugs devoid of negative inotropic set of ventricular tachycardia. In some drugs, primarily lidocaine. Thirty-three effects would increase the likelihood of these patients, it may be essential to patients received life-saving, successful of survival of some patients with the

JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 2, 1977 113 68:913-944,1941 3. Mintz S, Katz L: Recent myocardial infarction - an analysis of 572 cases. Arch Int Med 80:205-207, 1947 4. Smith J, Keyes J, Denhawn R: Myocardial infarction - a study of the acute phase in 920 habitants. Am J Med Sci 221:508-521, 1951 W. 5. Ball 0, Billings T, Furmain R; et al: A- The functional circulatory consequences of myocardial infarction - biostatistical analy- .ilil!Til.[z!.![~~~~~~PHifh?£tu lilr:,rI sis following Wigger's ischemia. Circulation Mi!lliIIW 11:749-753, 1955 M.~~~~~~~~~~~~~4s. 1kt lsN!-!lIIlllX!lillWdI[!l2". illiD l 6. Hurwitz M, Eliot RS: Arrhythmias in acute myocardial infarction. Dis Chest 45:616-626, 1964 LI'§''I.'I' I'i' ~~~1 PH1 7. Day H: Effectiveness of an intensive coronary care area. Am J Cardiol 15:51-54, 1965 8. 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The mortality tion complicating acute myocardial infarc- been applied in a preliminary study of rate was 37 percent but only two of tion. Am J Cardiol 27:347-351, 1971 20. Lowne D, Klein MD, Hershberger intervals between ectopic beats.28 The 42 deaths occurred in patients who PI: Coronary and pre-coronary care. Am J availability of new practical investi- were not in pump failure. Med 46:705-712, 1969 21. Dalle XS, Meltzer E, Kravitz D: A gative tools will make possible new new look at ventricular tachycardia. Acta Cardiol 22:519-524, 1967 insights into clinical arrhythmia mech- 22. Scherf D: Concerning paroxysmal anisms and classification, and will fa- tachycardia. Dis Chest 56:465-468, 1969 Acknowledgement cilitate therapeutic management. 23. Castellanos A, Lemberg I, Arcebal This investigation was supported by PHS AC: Mechanisms of slow ventricular tachy- Grant #HS00106 from the National Center cardia in acute myocardial infarction. 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Haywood LJ, Harvey GA, Saltzberg public hospital, an incidence of 34.2 2. Rosenbaum F, Levine S: Prognostic SA: Significance of interectopic intervals in value of various clinical and electrocardio- automated arrhythmia monitoring (ab- percent. The arrhythmia commonly graphic features of acute myocardial infarc- stract). J Assoc Advance Med Instrument appeared initially over the first four tion. I. Immediate prognosis. Arch Int Med 6:169-174, 1972

114 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 69, NO. 2, 1977