Natural history and clinical significance of arrhythmias after acute cardiac infarction

Atrial fibrillation and mortality in patients with acute myocardial infarction: a systematic overview and meta-analysis

Atrial fibrillation (AF) confers an increased risk of mortality in patients hospitalized for acute myocardial infarction (AMI). However, it is unclear whether new-onset and preexisting AF portend a different risk. We extracted data from studies that evaluated in-hospital mortality in patients with AMI and included information on cardiac rhythm. Overall, the risk of mortality was higher in patients with AF than in those in sinus rhythm (OR 2.00, 95 % CI: 1.93-2.08; P < 0.0001). Compared with patients who remained in sinus rhythm, the risk of death was increased in patients with new AF certain (sinus rhythm on admission, new AF during hospitalization, and history of no evidence of prior AF; OR 3.38, 95 % CI: 2.98-3.83; P < 0.0001), new AF uncertain (sinus rhythm on admission, AF during hospitalization, but no clear information about previous history of AF; OR 1.90, 95 % CI:1.83-1.98; P < 0.0001), and permanent AF (AF before and during hospitalization; OR 2.01, 95 % CI:1.70-2.38;P < 0.0001). In a meta-regression analysis, the risk of death was 87 % higher in patients with new AF certain than in those with permanent AF (P = 0.013) or AF uncertain (P = 0.003), and not dissimilar in patients with new AF uncertain and permanent AF (P = 0.706).

Location of acute myocardial infarction and associated arrhythmias and outcome

BACKGROUND

Cardiac arrhythmias and conduction abnormalities complicating acute myocardial infarction (AMI) have been associated with adverse prognosis in numerous reports. Small studies have frequently associated different arrhythmias with various distributions of myocardial infarctions. We analyzed a nationally representative hospital discharge database to evaluate the relationship between the location of AMI and the associated arrhythmias and conduction abnormalities and their impact on in-hospital mortality.

METHODS

We searched the National Hospital Discharge Survey database for patients with a diagnosis of AMI and collected data on the associated arrhythmias and conduction abnormalities. In-hospital death was used as end point for analysis.

RESULTS

A total of 21,807 patients, representing 2,632,217 hospital discharges in the United States, with a primary diagnosis of AMI from 1996 to 2003 were included in this analysis. Patients with inferior or posterior AMI were more likely to develop complete heart block compared to those with anterior or lateral AMI (3.7% vs 1.0%, hazard ratio [HR] = 3.9, p <or= 0.001), but less likely to die prior to hospital discharge (7.7% vs 11.3%, HR = 0.65, p <or= 0.001).

CONCLUSIONS

Patients with an inferior or posterior AMI are more likely to develop conduction system abnormalities when compared to patients with an anterior or lateral AMI. On the other hand, anterior or lateral MI is a significant predictor of in-hospital death.

Targeting the renin-angiotensin-aldosterone-system in atrial fibrillation: a shift from electrical to structural therapy?

Despite its increasing incidence and prevalence, treatment options in atrial fibrillation (AF) are far from ideal and often limited. After decades of focus on the electrical aspects of AF with unsatisfactory results, recent research is focusing increasingly on the atrial structural remodelling that underlies the development of AF in different pathological conditions, such as hypertension, heart failure, diabetes mellitus and coronary artery disease. The aim of this review is to provide a comprehensive overview of the role of the renin-angiotensin-aldosterone-system in AF and to highlight the clinical evidence on renin-angiotensin-aldosterone-system blockade as a therapeutic option in AF.

Importance of the time of onset of supraventricular tachyarrhythmias on prognosis of patients with acute myocardial infarction

It is known that left ventricular (LV) function, severity of coronary artery disease, and the presence of ventricular arrhythmias are major determinants of prognosis in patients surviving an acute myocardial infarction (AMI). However, little is known about the relationship between the time of onset of supraventricular tachyarrhythmias (SVTs) and mortality. Therefore, this study was carried out in a 48-months period on 131 patients with AMI who presented with SVT during hospitalization. Of these, 53 patients (40.5%) had arrhythmia within < 12 h of MI, while 78 patients (59.5%) had arrhythmia between 12 h and 4 days. The arrhythmias studied were atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia. The patients were similar for age, gender, coronary risk factors, creatine kinase-MB peak, cardioversion and LV function. Angiographic features for patients with the < 12-h onset of arrhythmia were: 86.7% of the patients had uniarterial lesions, 8.9% had biarterial lesions, and 4.4% had triarterial lesions. Patients with the 12-h-4-day onset had 16.1%, 53.2%, and 30.6% (p < or = 0.05) of the respective lesions. Inferior wall myocardial infarction was more frequent among patients with the earlier onset (60.4%), while patients with the later onset presented more anterior wall infarctions (50.0%). Only 11.3% of the patients with the earlier onset presented with severe in-hospital congestive heart failure (Killip classes III-IV), versus 62.8% of the patients with the later onset (p < or = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

The treatment of atrial fibrillation. An evaluation of drug therapy, electrical modalities and therapeutic considerations

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in clinical practice, and is responsible for considerable morbidity. Basic studies have shown that AF is usually due to the coexistence of multiple functional atrial re-entry circuits, and that the main determinant of its haemodynamic manifestations is the ventricular response rate. The major adverse clinical consequences of AF include palpitations, impaired cardiac function and thromboembolism. One approach to treating AF is to convert the patient's cardiac rhythm to sinus rhythm by direct current electrical cardioversion, which is initially successful in about 90% of cases. However, the AF recurrence rate over the year subsequent to cardioversion is very high, in the order of 75% in patients receiving no drug therapy. Class I and class III antiarrhythmic drugs reduce the rate of recurrence of AF, but at the expense of a variety of potential adverse effects including ventricular proarrhythmia. The latter is a rare effect (occurring in 1 to 2% of patients receiving most drugs), but can be lethal. A second approach to therapy is to leave the patient in AF, but to control the ventricular response rate and to prevent thromboemboli with oral anticoagulants. Disadvantages of this approach include the possibilities of functional limitations imposed by the arrhythmia, adverse effects of drug therapy, and major bleeding related to anticoagulation. New approaches currently under study include surgery to prevent AF from sustaining itself, implantable cardioverter devices to maintain sinus rhythm, and modification of AV nodal function by the induction of controlled radiofrequency injury.

Prognosis of acute myocardial infarction complicated by complete heart block (the Worcester Heart Attack Study)

As part of a community-based study of patients hospitalized with acute myocardial infarction (AMI) in the Worcester, Massachusetts, metropolitan area, changes over time in the incidence rates of complete heart block (CHB) complicating AMI, and the prognostic impact of CHB on the in-hospital and long-term survival of these patients were examined. In all, 4,762 patients with validated AMI hospitalized at 16 hospitals in the Worcester metropolitan area during 1975, 1978, 1981, 1984, 1986 and 1988 constituted the study sample. The incidence rates of CHB complicating AMI remained relatively stable at 5.8% over the 13-year (1975 to 1988) period studied. The incidence rates of CHB were approximately twice as high in patients with inferior/posterior wall AMI (7.7%) as in those with anterior wall AMI (3.9%). Use of a multivariate regression analysis to control for factors affecting the incidence rates of CHB revealed that patients were at highest risk for developing CHB during the latter 2 study years (1986 and 1988). Patients with AMI developing CHB had higher in-hospital case fatality rates than did those without CHB overall, as well as during each of the 6 periods studied. The in-hospital survival associated with CHB did not improve over time. After use of a multivariate regression analysis to control for additional prognostic factors, the independent effect of CHB on in-hospital prognosis remained (adjusted risk of dying = 2.10; 95% confidence intervals = 1.37, 3.21). Patients with inferior wall AMI complicated by CHB were at significantly increased risk of dying during hospitalization compared with those without CHB (adjusted risk of dying = 2.71; 95% confidence intervals = 1.60, 4.59).(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of atrial fibrillation on the in-hospital and long-term survival of patients with acute myocardial infarction: a community-wide perspective

As part of an ongoing community-wide study examining changes over time in the incidence and survival rates of 4108 patients hospitalized with validated acute myocardial infarction (MI) in 16 hospitals in the Worcester, Massachusetts, metropolitan area during calendar years 1975, 1978, 1981, 1984, and 1986, we examined changes over time in the proportion of patients with acute MI developing atrial fibrillation (AF) and the impact of AF on in-hospital and long-term survival for up to a 10-year follow-up period. The overall percentage of patients with AF complicating acute MI was 16.0%; this proportion increased over time from 13.3% in 1975 to 14.8% in 1978, 14.9% in 1981, 20.3% in 1984, and to 17.7% in 1986. Patients with AF experienced consistently higher in-hospital case fatality rates than MI patients without AF overall (27.6% versus 16.6%), as well as during each of the 5 years under study. The independent effect of AF on in-hospital survival was not upheld, however, when a variety of potentially confounding prognostic factors were controlled for in a multivariate analysis resulting in an adjusted odds ratio (OR) of 1.18 (95% confidence interval 0.90, 1.52). Among discharged hospital patients, while the crude long-term survival rate for patients with AF was poorer than that of patients without AF for the combined as well as for individual study periods, similar to the in-hospital findings the independent effect of AF on long-term prognosis was not upheld after use of a multivariate analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency, characteristics and significance of supraventricular tachyarrhythmias detected by 24-hour electrocardiographic recording in the late hospital phase of acute myocardial infarction

The incidence, characteristics and clinical significance of supraventricular tachyarrhythmias occurring in the late hospital phase of acute myocardial infarction (AMI) were assessed in 209 consecutive patients. Arrhythmias were quantified by 24-hour electrocardiographic recording 16 +/- 3 days after AMI, and were classified according to the degree of complexity in 5 classes. Class 0 = less than 5 premature beats/hr; class 1 = between 5 and 100/hr; class 2 = greater than 100/hr or repetitive premature beats; class 3 = atrial-junctional tachycardia; class 4 = atrial flutter-fibrillation. Supraventricular tachyarrhythmias classes 1 to 2 always occurred in the absence of symptoms in 86 patients (41%); supraventricular tachyarrhythmias classes 3 to 4 (paroxysmal, self-limiting, brief) occurred in 27 patients (13%), symptomatically in 6. The presence of supraventricular tachyarrhythmias classes 2 to 3 was related to age over 55 years and complex ventricular tachyarrhythmias (greater than 20 premature beats/hr, ventricular tachycardia) (both p less than 0.05). Increasing complexity of supraventricular tachyarrhythmias was significantly associated with presence and entity of cardiac enlargement and left ventricular dysfunction (both p less than 0.01). Patients with class 4 showed the most severe cardiac deterioration. During the 2 years after AMI, patients with classes 2, 3 and 4 had a higher incidence of acute pulmonary edema, New York Heart Association functional classes III to IV for congestive heart failure (both p less than 0.005) and a greater need of digitalis and diuretics (p = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic sinoatrial disorder (sick sinus syndrome): a possible result of cardiac ischaemia

Postmortem angiography was used to examine the blood vessels supplying the sinoatrial node in 25 subjects with chronic sinoatrial disorder (group 1). The results were compared with similar studies in 54 subjects who died of heart block and in whom sinus node function was normal (group 2). Although no significant lesion obstructing the blood flow to the sinus node was seen in the majority of those in group 1, there were abnormalities in seven cases, with reduced filling of the sinus node artery in five. In group 2 the sinus node artery filled normally in all cases despite major disease of the parent vessel in three. The combination of contralateral coronary artery disease with extensive atrial anastomoses was actively sought because this arrangement might predispose to a steal phenomenon. Such conditions were fully met in three cases in group 1 and two cases in group 2, and were found to a lesser extent in a further two cases in group 1 and three in group 2. Although coronary artery disease was unlikely to be the principal cause of sinus node dysfunction in most of the cases studied it was relatively common and may have been a factor in about one third. Improved survival after myocardial infarction may increase the number of patients with chronic sinoatrial disorder of ischaemic origin.

Atrial fibrillation--a marker for abnormal left ventricular function in coronary heart disease

Retrospective study of 1176 patients with known coronary heart disease by cardiac catheterisation disclosed 10 patients (0.8%) with atrial fibrillation. Comparison with 25 randomly selected patients with coronary heart disease with sinus rhythm showed that atrial fibrillation correlated significantly with impaired haemodynamic function, mitral regurgitation, and abnormalities of left ventricular contraction. Atrial fibrillation is, therefore, a useful marker of extensive myocardial dysfunction.

His-bundle electrogram in the convalescent stage of inferior myocardial infarction complicated with complete A-V block

Twelve patients with inferior wall myocardial infarction complicated with complete atrioventricular block during the acute stage were studied. The His-bundle electrogram was studied in the convalescent stage at an average of 6 months after the acute attack. The age of the patients was 62 +/- 16 years. The width of the QRS complex was within the normal range and the PR interval was less than 200 msec. AH time was 74 +/- 18 msec (mean +/- SD). No split H activity was observed. HV time however, was significantly prolonged in the 12 patients; 54 +/- 12 msec vs. 42 +/- 9 msec in the control group (p less than 0.02). Five patients had HV time equal to or more than 60 msec. Intra-His block was suggested to exist in a high frequency in the patients who had previous complete AV block during the acute stage of myocardial infarction of the inferior wall.

The management of arrhythmias following an acute myocardial infarction

Arrhythmias are extremely common early after AMI. An arrhythmia is defined by exclusion, either because the sequence of myocardial depolarisation is other than normal or because certain arbitrary limits are exceeded. It follows that the term "arrhythmia" encompasses a complex heterogenous group. Although arrhythmias are defined in electrical terms they are only important because of their immediate, delayed or potential haemodynamic consequences. These occur because of changes in heart rate, loss of atrial transport function, increased myocardial oxygen consumption, decreased myocardial blood flow or loss os synchronicity of ventricular contraction. The sensible and effective management of arrhythmias following acute myocardial infarction requires an appraisal of the haemodynamic consequences, if any, which follow the initiation of the arrythmia. The indications for treating an arrhythmia must be the immediate, delayed or potential haemodynamic loss rather than the mere presence of a rhythm which falls outside the limits of normal. This distinction is perhaps most clearly seen in the case of atrio-ventricular conduction disturbances.

Small animal model for myocardial infarction

Myocardial infarctions were produced in rats by electro-cauterization of the left anterior descending artery, and the extent of myocardial damage was measured by serial serum levels of creatine phosphokinase activity utilizing spectrophotometric analysis. All animals were also evaluated for myocardial damage by electrocardiographic wave alterations. A correlation between myocardial infarct size and serum creatine phosphokinase was demonstrated. Significant arrhythmias and death occurred only in experimental groups where myocardial infarction had been produced. This small animal model offers a quick, inexpensive, and simple method for screening therapeutic agents that alter infarct size.

Origin of ventricular reflexes caused by coronary arteriography

Left ventricular reflexes have in the past been investigated in anaesthetised animals, generally using an open chest technique. We have studied the degree of bradycardia occurring during coronary arteriography in 200 patients with a view to localising the origin of the ventricular reflexes. We have correlated the decrease of sinus rate with the anatomical distribution and integrity of the coronary tree. The degree of bradycardia was not influenced by the origin of the sinus node or the AV node arteries, while there was a good correlation with the injection of contrast medium into the artery which supplied the inferior wall of the left ventricle. The occurrence of transient sinus arrest was also correlated with the injection into the same artery. The results suggest that the parasympathetic receptors are located mainly in the inferior wall of the left ventricle. This may well be the explanation for the clinical picture of bradycardia, hypotension, and peripheral vasodilatation often seen in acute inferior myocardial infarction.

Pathological studies in sinoatrial disorder (sick sinus syndrome)

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Histopathology of the conduction system in patients with atrioventricular or intraventricular conduction disturbances

In 9 lethal cases where clinical signs gave rise to the suspicion of acute myocardial infarct (AMI) where well-characterized e.c.g.-changes, permanent or intermittent, were found by monitoring, a very careful autopsy of the heart was carried out, combined with a meticulous histological investigation of the conduction system. Acute changes of mild degree in the conduction system were found only in one case, possibly explaining the left bundle branch block found in this case. In the remaining cases, nothing but chronic changes were found and they did not exceed significantly the changes otherwise to be found in the agegroups concerned in a "control series" of violent deaths not preceded by symptoms of heart disease. According to an estimate there was good correlation between the conduction disturbances demonstrated and the localization of histopathological changes in seven of nine patients; in one of the latter correlation was relatively good; correlation was dubious only in one case. On this basis the authors conclude that present changes in the conduction system which are assumed mainly to be age-related, are the factors to determine the type of conduction disturbances from which the patient will suffer if acute heart ischaemia sets in, for instance due to an AMI, in fact, changes by which he will be predisposed to such disturbances.

Prognostic importance of ventricular extrasystoles in acute myocardial infarction

Ventricular arrhythmias were recorded in 233 patients in a prospective study of patients with acute myocardial infarction. In over 95% of patients antiarrhythmic therapy was not given until the onset of ventricular tachycardia, ventricular fibrillation, or persistent idioventricular rhythm. There was a mortality of 18% during the patients' stay in hospital. The most important features of ventricular ectopic activity, which preceded these severe ventricular arrhythmias in the first 48 hr, were multiformity, variation of coupling intervals of larger or equal to 0-1 sec, the R-on-T phenomenon, double ventricular extrasystoles and ventricular bigeminy. The number of a single ventricular extrasystoles per minute was related to the probability of these severe ventricular arrhythmias but to a lesser degree. It was found that if all the patients with the first two prognostic features that if all the patients with the first two prognostic features were removed, the number of single ventricular extrasystoles was not of significant import and the other features were less important. Three-quarters of the severe arrhythmias occurred in the first 24 hr and during this period 60% were preceded by either multiform ventricular extrasystoles or extrasystoles with variable coupling. The importance of these findings in relation to prophylactic therapy is discussed.

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 (16/39). Atrial fibrillation was more common in patients with undetermined infarctions and 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 affect the mortality among patients with inferior infarctions (10 percent, 1/10). Ventricular rates higher than 120 beats per minute and duration of the arrhythmia longer than six hours were not associated with increased mortality. Hemodynamic failure 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 infarction, and the prognosis of the patient is related to the mechanism of production and not to the arrhythmia itself.

Atrial tachyarrhythmias in acute myocardial infarction

Causative factors, clinical consequences and treatment of atrial tachyarrhythmias were reviewed in 917 monitored patients with definite acute myocardial infarction. Significant atrial tachyarrhythmias were found in 104 (11 per cent) of them and included atrial fibrillation in 67, atrial flutter in 29 and paroxysmal atrial tachycardia in 33. These episodes were single in 79 patients and multiple in 25, and began within the first four days of acute myocardial infarction in 90 per cent of the patients. Fifty per cent of these atrial tachyarrhythmias were heralded by premature atrial contractions. The incidence of atrial tachyarrhythmia was not related to the location of the acute myocardial infarction or to the presence or degree of power failure; however, atrial tachyarrhythmias were significantly more frequent in patients with pericarditis. Atrial tachyarrhythmias were well tolerated in almost one fifth of the patients, caused marginal compromise in almost two thirds and led to severe clinical deterioration in one fifth. Paroxysmal atrial tachycardia rarely required specific treatment, atrial fibrillation was best managed with intravenous administration of digoxin except when associated with severe clinical compromise, and atrial flutter generally required cardioversion or rapid intravenous therapy and usually caused severe clinical deterioration. Over-all, atrial tachyarrhythmia was not associated with a significantly increased mortality, and in those who died, death was not related specifically to the atrial tachyarrhythmia but rather to the severity of the underlying acute myocardial infarction. However, persisting atrial tachyarrhythmias, particularly atrial flutter which tends to be refractory to both heart rate control and cardioversion, may contribute indirectly to morbidity and mortality.

Relation of ventricular arrhythmias in the late hospital phase of acute myocardial infarction to sudden death after hospital discharge

To determine the prognostic significance of ventricular arrhythmias persisting during the hospital ambulatory phase of acute myocardial infarction, 64 patients with acute myocardial infarction underwent continuous 10-hour Holter monitoring an average of 11 days after discharge from the coronary care unit (CCU). Patients were categorized according to the results of ambulatory monitoring: 27 patients had ventricular extrasystoles, which were complicated (multifocal, R on T, paired, more than 5/min), or ventricular tachycardia; 22 had uncomplicated premature ventricular contractions; and 15 exhibited no ventricular arrhythmias. The 64 patients were followed prospectively for an average course of 25.8 months; 12 died suddenly; 8 died of other causes, and 44 survived. In all patients who died suddenly, ventricular ectopy was recorded on Holter monitoring before their discharge from the hospital (complicated premature ventricular contractions, eight patients; uncomplicated premature ventricular contractions, four patients); there were no sudden deaths in the patients without ventricular arrhythmias. Patients who died suddenly and those survived were similar in respect to age (60, 62 years), sex, location of infarction, presence of coronary risk factors, severity of acute myocardial infarction (Q waves, cardiac enzymes), serum cholesterol levels, evidence of cardiomegaly on roentgenograms, presence of ventricular gallop and drug therapy received. The occurrence of acute arrhythmias in the CCU did not separate patients who died suddenly from those who survived; there were no differences in ventricular tachycardia or ventricular fibrillation (3 or 12 patients who died suddenly, 6 of 44 patients who survived) or complicated premature ventricular contractions (4 or 12 patients who died suddenly, 18 of 44 patients who survived). Electrocardiograms obtained late in the hospital course revealed no differences in the extent of Q or T wave changes between these two groups. However, the extent of S-T segment abnormality was greater in patients who died suddenly than in patients who survived (5.6 compared to 1.8 leads/standard tracing, p smaller than 0.02) suggesting that the arrhythmias in the former were related to persistent ischemia or segmental ventricular dyssynergy. Thus, in this relatively small number of patients, ventricular arrhythmias persisting late in the hospital course of patients admitted for acute myocardial infarction are shown to predispose to subsequent sudden death.

Evaluation of arrhythmias in the late hospital phase of acute myocardial infarction compared to coronary care unit ectopy

To evaluate the prevalence and nature of arrhythmias during the entire three-week period in hospital after myocardial infarction, the results of coronary care unit monitoring (initial 3 to 5 days) were compared with continuous 8-hour portable monitoring during the ambulatory phase (second and third weeks) in 83 consecutive survivors. Arrhythmias were detected in 84.3 per cent (70/83) of patients while in the coronary care unit and in 85.5 per cent (71/83) during hospital stay after the coronary care unit. Ventricular ectopic depolarizations were classified as complicated (multifocal, paired, R on T, or five or more a minute) or uncomplicated. Importantly, the high frequency of complicated ventricular extrasystoles and tachycardia persisted during the entire period in hospital (early 34.9% and late 42.5% of all patients). However, only 16.9 per cent (14/83)had these ventricular arrhythmias during both coronary care unit and ward monitoring. Thus, the absence of complicated ventricular ectopic depolarization and ventricular tachycardia in the coronary care unit did not exclude their subsequent occurrence in the majority of the large number of patients with late hospital complicated ventricular ectopy.

Sinus bradycardia

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The value of monitoring pulmonary artery pressure for early detection of left ventricular failure following myocardial infarction

Flow-directed catheters recorded serial changes in mean pulmonary artery pressure (PA) every 4 to 6 hours in 25 patients during the first 4 or 5 days following acute myocardial infarction. On the basis of the PA on admission, patients were divided into three groups. Patients in group 1 had normal PA (10-20 mm Hg) and maintained a stroke volume index (SVI)>35 ml/min/m 2 , a pulmonary artery oxygen saturation (MVSO 2 )>70%, and a normal cardiac index, arterial oxygen saturation, p H, and P CO CO2 . They developed only minor arrhythmias, no heart failure, and none died. Group 3 consisted of one patient with abnormally low PA (<10 mm Hg) who was hypovolemic. Group 2, those patients with elevated PA (>20 mm Hg) who maintained this elevation over the first 48 hours of monitoring, or showed progressive elevation prior to this, had SVI<35 ml/min/m 2 , MVSO 2 <70%, cardiac index<3 liters/min/m 2 , arterial desaturation, and respiratory alkalosis. They demonstrated clinical evidence of heart failure, had major arrhythmias, and 25% died. Three patients with elevated PA on admission spontaneously returned this pressure to normal over the first 48 hours of monitoring. Each of these patients maintained normal hemodynamics and had a good prognosis. PA was always elevated prior to the usual clinical signs of left ventricular failure. We conclude that PA provides a reliable early objective measure of left ventricular failure and is, therefore, an excellent guide to therapy.

A review of experience operating a general medical intensive care unit

From 18 months' experience of operating a four-bedded general medical intensive care unit a high staff-to-patient ratio was the most important factor in its success. Heavy capital spending does not appreciably reduce the importance of adequate numbers of trained staff, though patient-monitoring equipment can be useful and sometimes vital. As the scope for intensive care widens, the problems of clinical care become difficult, because no doctor is likely to be competent enough to provide for all categories of patients, and there is no intensive care equivalent of the general physician. Intensive care is likely to function best in a divisional specialist system of clinical care.

Immediate effect on cardiac output of reversion to sinus rhythm from rapid arrhythmias

Cardiac output was estimated immediately before and after conversion to sinus rhythm in nine patients with rapid arrhythmias. Conversion was by synchronized direct-current shock in eight patients, and by direct atrial wall stimulation in the other. In seven patients there was an immediate increase in cardiac output after restoration of sinus rhythm. The percentage increase in output was directly proportional to the rate of the arrhythmia immediately before conversion (r=0.91, P<0.01). The critical heart rate, above which an immediate increase in cardiac output might be expected on conversion to sinus rhythm, appeared in these patients to be about 160 beats per minute.

Incidence and management of ventricular arrhythmias after acute myocardial infarction

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