Incidence of persistent atrial fibrillation and conduction defects in coronary heart disease

Echocardiographic left atrial dimension as a predictor of maintaining sinus rhythm after conversion of atrial fibrillation

Twenty-six patients with lone atrial fibrillation were studied prospectively by M-mode echocardiography less than two months before and one month after cardioversion (CV). Seven patients had reverted to atrial fibrillation (AF) one month after CV. These patients (AF group) differed significantly with regard to mean left atrial dimension (LA) from the 19 patients (73%) who maintained sinus rhythm (S group) (p less than 0.001). Initial LA was 38.6 +/- 4.9 mm in the S group and 47.6 +/- 2.3 mm in the AF group. These values had not changed significantly in either group when measured one month after CV. The radiological heart size index showed a closely corresponding pattern. On the other hand, the mean heart size in both groups (441 +/- 100 and 544 +/- 98 ml/m2 BSA, respectively) was well below the upper normal limit (700 ml/m2) that is conventionally used as exclusion criterion from CV. In conclusion, in patients with AF and only moderate cardiac enlargement on chest X-ray, the echocardiographic LA can be used as predictor of maintaining sinus rhythm for at least one month following CV.

Atrial fibrillation--a review of course and prognosis

Four recent major studies concerning the prognosis in atrial fibrillation (AF) are reviewed. The one-year mortality ranged from 16.0 to 0.2%, highest in elderly, hospitalized patients with chronic AF and lowest in young individuals with paroxysmal AF without other heart disease. The recognized clinical impression that the prognosis in AF is determined by age, type of AF and clinical status is thus confirmed. In three studies, however, the prognosis in lone atrial fibrillation seemed to be poorer than previously thought. The overall rate of thromboembolic complications in AF was about 25% in several studies. The effectiveness of coumarin drugs in the prophylaxis of these complications is not proved, and the time has come to subject them to more careful clinical investigation.

Coronary ischemic events after first atrial fibrillation: risk and survival

PURPOSE

We aimed to determine the long-term, gender-specific incidence and mortality risk of coronary ischemic events after first atrial fibrillation (AF).

METHODS

In this longitudinal cohort study, adult residents of Olmsted County, Minnesota, with an electrocardiogram-confirmed AF first documented in 1980 to 2000 and without prior coronary heart disease, were followed to 2004. The primary outcome was first coronary events (angina with angiographic confirmation, unstable angina, nonfatal myocardial infarction, or coronary death). Sex-specific incidence of coronary ischemic events and survival after development of such events were assessed using Cox proportional hazards modeling. Kaplan-Meier estimates of risks for coronary ischemic events were compared with those predicted by the Framingham equation.

RESULTS

Of the 2768 subjects (mean age 71 years, 48% were men), 463 (17%) had a first coronary event during a follow-up of 6.0+/-5.2 years. The unadjusted incidence was 31 per 1000 person-years, and there was no difference between men and women. The incidence was higher in men (hazard ratio 1.32, P=.004) after adjusting for age. The 10-year event estimates were 22% and 19% in men and women, respectively, by our Kaplan-Meier analyses, and 21% and 11%, respectively, by Framingham risk equation. The mortality risk after coronary events was higher in women (hazard ratio 2.99 vs 2.33; P=.044), even after multiple adjustment.

CONCLUSIONS

First AF marks a high risk for new coronary ischemic events in both men and women. AF conferred additional risk for coronary events beyond conventional risk prediction in women only. The excess mortality risk associated with the development of coronary events was significantly greater in women.

Intravenously administered digoxin in patients with acute atrial fibrillation: a population pharmacokinetic/pharmacodynamic analysis based on the Digitalis in Acute Atrial Fibrillation trial

OBJECTIVE

Atrial fibrillation is commonly treated with intravenously administered digoxin. The main objective of this study was to investigate the relationship between plasma concentration of digoxin and heart rate.

SUBJECTS AND METHODS

Plasma concentrations of digoxin were analysed in 105 patients allocated to digoxin therapy in the Digitalis in Acute Atrial Fibrillation (DAAF) trial. A pharmacokinetic/pharmacodynamic (PK/PD) model for the relationship among digoxin dose, plasma concentration and heart rate in patients remaining in atrial fibrillation was constructed using non-linear, mixed-effect modelling. One hundred and twenty-two placebo-treated patients were included as a control group. In 56 patients, one late sample at 16 h after the first dose of digoxin was obtained while in 49 patients an early sample at 0.25-0.5 h and a late sample 16 h after the first dose were obtained. Heart rate was measured at 0, 2, 6, 12 and 16 h after inclusion, with data from 98, 89, 67, 56 and 53 patients available at each time point, respectively.

RESULTS

A two-compartment model best described the time course of digoxin concentrations in plasma. Digoxin and creatinine clearance correlated strongly and mean plasma concentration of digoxin at 16 h was within recommended levels (1.6+/-1.0 nM). The decrease in heart rate in placebo-treated patients was, on average, 0.5 beats/min (bpm) per hour. In patients on digoxin, a linear relationship between the estimated digoxin concentration at the effect site and the drop-in heart rate was found. The half-life for the digoxin distribution to the effect compartment was approximately 3.8 h. The degree of reduction was related to the initial heart rate and patients with higher heart rate had a more pronounced decrease. The model predicted that a digoxin concentration of 1 nM at the effect site reduces heart rate by 9.4%.

CONCLUSION

A PK/PD model for the relationship between the plasma concentration of digoxin, the estimated concentration at the effect site and the reduction in heart rate during atrial fibrillation could be defined using a population pharmacokinetic approach. Our data indicate that a more aggressive dosing regimen of digoxin may be more effective in terms of heart rate reduction.

Risk of thromboembolism in acute atrial fibrillation or atrial flutter

Atrial fibrillation (AF) is the most common sustained cardiac dysrhythmia, predominating in the elderly, with stroke as a potentially devastating complication. Prevention of the thromboembolic sequelae from AF remains a central focus of practicing clinicians. Although the risk of thromboembolism in chronic AF is well recognized, less is known about the potential risk of systemic embolism in acute AF. In addition, recent data support the notion of a group at considerable risk of embolism from atrial flutter, an arrhythmia typically believed to bestow little increased risk of thromboembolism. The mechanism of thrombus formation, embolization, and resolution in atrial arrhythmias is not well defined, particularly in that of acute AF or atrial flutter. The traditional concept proposes that atrial thrombus forms only after > 2 days of AF and embolizes by being dislodged from increases in shear forces. This widely accepted concept further holds that newly formed atrial thrombus, in the setting of AF, organizes over a span of 14 days. The results of studies based on observations from transesophageal echocardiography examinations have provided provocative insight into the temporal sequence of atrial thrombus formation, embolization, and resolution in AF or atrial flutter and have expanded the traditional concept of thromboembolism in these atrial dysrhythmias. Namely, left atrial thrombus may form before the onset of AF in the face of sinus rhythm. Conversion to sinus rhythm may increase the thrombogenic milieu of the left atrium. Importantly, atrial thrombus may form in the acute phase of AF. Last, thrombi may require > 14 days to become immobile or to resolve. Findings similar to those of acute AF have been reported in patients with atrial flutter and coexisting cardiac pathology. On the basis of these emerging insights fostered by the use of transesophageal echocardiography, it appears appropriate to consider anticoagulation in patients presenting with acute AF or atrial flutter with coexisting cardiac pathology predisposing to left atrial thrombus.

Is anticoagulation therapy underused in elderly patients with atrial fibrillation?

Atrial fibrillation (AF) is found in 0.4% of the adult population and is a common condition in the elderly. Its prevalence increases with age to affect 5 to 14% of those over 74 years. Recent evidence indicates that, compared with sinus rhythm, AF is associated with a 4-to 7-fold increase in the risk of stroke. However, there is strong evidence from randomised trials that full anticoagulation with warfarin substantially reduces the risk of stroke. Elderly patients are among those at higher risk and stand to gain the most from such treatment. They are also at higher risk for complications related to anticoagulant therapy and this sometimes makes clinical decisions difficult. There is a strong rationale for prescribing warfarin for all patients with AF who are over 65 years and free of contraindications. Some concerns exist about the benefit: risk ratio of warfarin in patients aged > 75 years. The answer is probably to use low intensity anticoagulant therapy (international normalised ratio 2.0 to 3.0), which is safer but no less effective than higher intensity regimens. Few data are available in the literature on physicians' attitudes to anticoagulation in elderly patients with AF. Although the results of randomised clinical trials in AF seem to suggest that anticoagulants and/or aspirin (acetylsalicylic acid) are underused in the elderly, over 90% of the patients initially screened were excluded from randomisation, making the sample highly selected. Compared with randomised controlled trials, some observational studies seem to indicate a higher likelihood of using anticoagulation and have targeted the intensity of anticoagulation according to age and clinical scenario.

Risk of thromboembolism in new onset or transient atrial fibrillation

Atrial fibrillation (AF), potentially serious cardiac arrhythmia, occurs in 2% to 4% of persons greater than 60 years of age. The risk of systemic thromboembolism from chronic AF has long been recognized. Little is known about the thromboembolic risk of new onset AF. However, the results of prior studies support a significant risk of thromboembolism because of recent onset or paroxysmal AF. The mechanism of thrombus formation, embolization, and resolution in AF is ill-defined, particularly that of new onset. The traditional concept holds that atrial thrombus forms only after greater than 2 days of AF and embolizes by dislodgement from increases in shear forces. This prevailing concept further proposes that newly formed atrial thrombus, in the setting of AF, organizes over a span of 14 days. The results of recent transesophageal echocardiographic studies have given insight into the temporal sequence of atrial thrombus formation, embolization, and resolution in AF and have expanded the traditional concept of thromboembolism in AF. Namely, left atrial thrombus may form before the onset of AF in the face of sinus rhythm. Conversion to sinus rhythm may increase the thrombogenic millieu of the left atrium. Importantly, atrial thrombus may form in the acute phase of AF. Lastly, thrombus may require more than 14 days to become immobile or to resolve. On the basis of these emerging insights by transesophageal echocardiography, it appears appropriate to consider anticoagulation in patients presenting with new onset or acute AF.

Transesophageal echocardiographic guidance of cardioversion in patients with atrial fibrillation

The role of TEE in the guidance of cardioversion of atrial fibrillation was studied. Thirty-seven (18%) of 206 patients had left atrial thrombus. Cardioversion was attempted in 153 patients receiving no (n = 107) or < 7 days (n = 46) of anticoagulation prophylaxis, in 27 patients after > or = 3 weeks of anticoagulation, and was cancelled in 26 patients, primarily on the basis of TEE findings. Left atrial thrombus was observed in 37 (18%) of 206 patients. No embolic complications occurred over a 4-week follow-up period. In 7 (41%) of 17 patients new left atrial appendage spontaneous echocardiographic contrast developed immediately after electric cardioversion. In this group, significant decreases occurred in the left atrial appendage maximal emptying shear rate (11.1 +/- 11.1 sec-1 vs 5.0 +/- 5.1 sec-1; p < 0.05), maximal filling shear rate (6.7 +/- 5.9 sec-1 vs 3.7 +/- 3.5 sec-1; p < 0.05), and peak emptying velocity (0.38 +/- 0.29 cm/sec vs 0.19 +/- 0.14 cm/sec; p < 0.05). In one patient a left atrial appendage thrombus formed after electric cardioversion. Left atrial thrombus resolved in 1 (5%) of 21 patients and became immobile in 0 (0%) of 16 patients after 3 to 5 weeks of anticoagulation but resolved (n = 9) or became immobile (n = 6) in 15 (71%) of 21 patients after > 5 weeks of anticoagulation. TEE-guided cardioversion was safely done without or with < 7 days of anticoagulation prophylaxis in selected patients, but the potential for left atrial thrombus to form after electric cardioversion makes anticoagulation advisable in all patients. The conventional recommendation of 3 to 4 weeks of anticoagulation prophylaxis before cardioversion is usually inadequate for left atrial thrombus to resolve or to become immobile.

Left atrial appendage thrombus is not uncommon in patients with acute atrial fibrillation and a recent embolic event: a transesophageal echocardiographic study

OBJECTIVES

The objective of this study was to determine the frequency of left atrial thrombus in patients with acute atrial fibrillation.

BACKGROUND

It is commonly assumed but unproved that left atrial thrombus in patients with atrial fibrillation begins to form after the onset of atrial fibrillation and that it requires > or = 3 days to form. Thus, patients with acute atrial fibrillation (i.e., < 3 days) frequently undergo cardioversion without anticoagulation prophylaxis.

METHODS

Three hundred seventeen patients (250 men, 67 women; mean [+/- SD] age 64 +/- 12 years) with acute (n = 143) or chronic (n = 174) atrial fibrillation were studied by two-dimensional transesophageal echocardiography.

RESULTS

Left atrial appendage thrombus was present in 20 patients (14%) with acute and 47 patients (27%, p < 0.01) with chronic atrial fibrillation. In patients with a recent embolic event, the frequency of left atrial appendage thrombus did not differ between those with acute (5 [21%] of 24) and those with chronic (12 [23%] of 52, p = NS) atrial fibrillation. Patients with acute versus chronic atrial fibrillation, respectively, did not differ (p = NS) in mean age (64 +/- 13 vs. 65 +/- 11 years), frequency of concentric left ventricular hypertrophy (32% vs. 26%), hypertension (32% vs. 41%), coronary artery disease (35% vs. 39%), congestive heart failure (43% vs. 48%), mitral stenosis (4% vs. 7%) or mitral valve replacement (1.4% vs. 6%). The minimally detectable difference in proportions between patients with acute and chronic atrial fibrillation based on a power of 0.80 and base proportion of 0.20 was 14%.

CONCLUSIONS

Left atrial thrombus does occur in patients with acute atrial fibrillation < 3 days in duration. The frequency of left atrial thrombus in patients with recent emboli is comparable between those with acute and chronic atrial fibrillation. These data suggest that patients with acute atrial fibrillation for < 3 days require anticoagulation prophylaxis or evaluation by transesophageal echocardiography before cardioversion and should not be assumed to be free of left atrial thrombus.

Lone atrial fibrillation and anticoagulant therapy

Assessment of risk of thromboembolism and potential benefit of prophylaxis with long-term anticoagulant therapy in lone atrial fibrillation is hampered by a lack of consensus regarding definition of lone atrial fibrillation. In general, patients less than 60 years of age with normal left ventricular function and left atrial size have a low risk of thromboembolic events and are unlikely to gain any significant benefit with anticoagulants; however, patients older than 60 years with impaired left ventricular function, enlarged left atrium, and/or associated conditions such as hypertension have an increased risk of thromboembolism and would benefit from long-term anticoagulant therapy. Decisions regarding anticoagulant usage would be simplified by using a scoring system containing clinical and investigational variables.

Placebo controlled trial of xamoterol versus digoxin in chronic atrial fibrillation

Thirteen patients in chronic atrial fibrillation with a normal resting heart rate but with exercise tachycardia and episodes of bradycardia were randomised to treatment periods of two weeks on xamoterol (200 mg twice daily), low dose digoxin, or placebo, in a blind crossover study. The results (mean SEM) of symptom scores, a treadmill exercise test, and 24 hour ambulatory electrocardiographic monitoring were obtained. Xamoterol improved symptom scores and controlled exercise heart rate better than digoxin. Xamoterol was better than digoxin or placebo in reducing the heart rate response to exercise and tended to improve exercise duration. Xamoterol, by reducing the daytime maximum hourly heart rate and increasing the night time minimum hourly heart rate, significantly reduced the difference between the two compared with placebo. In contrast, digoxin tended to reduce both the maximum and minimum hourly heart rates through day and night. Both the frequency and duration of ventricular pauses were reduced by xamoterol but tended to increase with digoxin. Xamoterol reduced both the circadian variation in ventricular response to atrial fibrillation and exercise tachycardia by modulating the heart rate according to the prevailing level of sympathetic activity. These changes were translated into symptomatic benefit for the patients studied.

Is atrial fibrillation an independent risk factor for stroke?

That non-rheumatic atrial fibrillation is an independent risk factor for cerebral infarction has not been established with certainty. The rationale underlying contemporary clinical trials of warfarin therapy for the prevention of stroke in patients who have non-rheumatic atrial fibrillation is that the majority of strokes in such patients are due to cardiogenic cerebral embolism. However, there is evidence to suggest that the increased probability of stroke attributed to this arrhythmia is due to its association with other risk factors such as hypertension, diabetes mellitus, and atherosclerosis. The question of who should be anticoagulated is a major public health issue since atrial fibrillation is present in approximately ten per cent of the general population aged 65 or more years.

Prevalence of cardiovascular disease and diabetes mellitus in residents of Rochester, Minnesota

To determine the prevalence of cardiac disorders as risk factors for stroke, we conducted a survey in 1986 in a stratified random sample of the population of Rochester, Minnesota, 35 years of age or older. The medical records of the 2,122 subjects in the sample were retrieved with use of the Rochester Epidemiology Project medical records linkage system. The data were used to estimate (1) the reliability of self-reported information about cardiac and cerebrovascular disorders and (2) the age- and sex-specific prevalence of diabetes mellitus and various cardiac and cerebrovascular conditions. The estimated prevalence for selected risk factors in the population 35 years of age or older was 5.8% for diabetes mellitus, 3.3% for myocardial infarction, 1.2% for mitral valve disease, 4.2% for left ventricular hypertrophy, and 2.8% for atrial fibrillation or flutter. These data can be used to estimate resources required for evaluation and management of the disorders. When the prevalence and the relative risk for stroke are known for a particular cardiac disorder, the proportion of stroke attributable to that disorder can be estimated.

Thromboembolic complications in atrial fibrillation

I review the present understanding of thromboembolic complications and their prevention in patients with nonrheumatic atrial fibrillation. Chronic atrial fibrillation carries an annual 3-6% risk of thromboembolic complications, which is 5-7 times greater than that of controls with sinus rhythm. Paroxysmal atrial fibrillation is associated with a lower risk of thromboembolic complications than chronic atrial fibrillation. Heart failure and systemic hypertension seem to be significant clinical risk factors for stroke in patients with atrial fibrillation, but disagreement persists, and, with few exceptions, subgroups at particular risk have not been convincingly identified. The risk of stroke in persons with thyrotoxic atrial fibrillation seems to be lower than believed previously. Clinical studies have shown that left atrial dilatation is a consequence of the duration of atrial fibrillation rather than a cause, but the relation of left atrial enlargement to stroke is uncertain. Cerebral blood flow may be reduced during atrial fibrillation but seems to increase after cardioversion to sinus rhythm. A high prevalence of silent cerebral infarction has been detected in patients with chronic atrial fibrillation, but there seems to be a low risk of silent cerebral infarction in persons with paroxysmal atrial fibrillation. The one prospective study published to date on stroke prevention in patients with nonrheumatic chronic atrial fibrillation showed that anticoagulation with warfarin significantly reduced the incidence of thromboembolic complications.

Prevalence and significance of atrial fibrillation in coronary artery disease (CASS Registry)

Estimates of the prevalence of atrial fibrillation (AF) in patients with coronary artery disease have varied from "frequent" to less than 2%. Data on 18,343 patients with angiographically demonstrated CAD in the Coronary Artery Surgery Study (CASS) registry were reviewed and AF was found to be present in 116 (0.6%) patients. The presence of AF was positively associated with the following clinical and angiographic variables: older age, sex (male), mitral regurgitation and functional impairment due to congestive heart failure. The number of diseased coronary arteries was negatively related to the presence of AF. Atrial fibrillation was an independent predictor of survival and its presence doubled the estimated risk over those patients without AF.

Stroke in thyrotoxicosis with atrial fibrillation

Chronic atrial fibrillation is associated with an increased risk of stroke. In elderly patients with thyrotoxicosis, atrial fibrillation is frequently encountered, and the true risk of cerebrovascular events in these patients is controversial. We retrospectively studied 610 patients with initially untreated thyrotoxicosis, 91 (14.9%) of whom had atrial fibrillation, with the highest frequency in the elderly patients. The risk of cerebrovascular events, with special attention to the first year after the diagnosis of thyrotoxicosis, was calculated using logistic regression methods with age, sex, and atrial fibrillation as independent variables. Only age was an important risk factor (p less than 0.005), whereas sex and atrial fibrillation were not significant (p = 0.09 and p = 0.17, respectively) as independent risk factors. This is contrary to other studies of patients with thyrotoxic atrial fibrillation, and the need for further clarification of this issue is clear. From our study the indication for prophylactic treatment with anticoagulants for prevention of stroke in thyrotoxic atrial fibrillation seems doubtful, especially as no controlled studies of such treatment in patients with atrial fibrillation are currently available.

Embolic complications in paroxysmal atrial fibrillation

The incidence of embolic complications among 426 patients with initial paroxysmal atrial fibrillation (PAF) was analysed. A distinct clustering of emboli was seen at the time of onset of PAF. After transition to chronic atrial fibrillation (CAF), which developed in 141 patients (33.1%), the incidence of emboli was seen to rise to a new level several times higher than the incidence level for patients with PAF. Also in this group a distinct clustering of emboli was seen during the first year after transition to CAF. On this background it is suggested that patients with PAF may benefit from treatment with anti-arrhythmic agents in order to prevent the development of CAF and that anticoagulants for stroke prevention seems especially desirable in atrial fibrillation (AF) of recent onset.

New-onset atrial fibrillation: is there need for emergent hospitalization?

Patients with new-onset atrial fibrillation are often hospitalized emergently. To determine whether this is necessary, the authors retrospectively reviewed the care of 97 consecutive patients with this illness. No reason for the atrial fibrillation in 43 patients could be identified. Hypertension, coronary artery disease, and valvular heart disease were the most commonly associated conditions; myocardial infarction occurred in one patient. In 82% of patients, atrial fibrillation reverted to normal sinus rhythm during hospitalization. Three patients needed emergent hospitalization irrespective of the presence of atrial fibrillation. In the remainder, admission was based solely on the diagnosis of new-onset atrial fibrillation. Ninety-eight per cent had an uncomplicated hospital course. It is concluded that hospitalization is not necessary for all patients with new-onset atrial fibrillation. Those in whom reversion to normal sinus rhythm occurs rapidly during digoxin therapy can be discharged. Where no major medical illness is evident patients can be admitted to a bed outside the intensive care unit until reversion to normal sinus rhythm or rate control is achieved.

Progress study of 590 consecutive nonsurgical cases of coronary disease followed 5-9 years. II. Ventriculographic and other correlations

The clinical progress was studied in a series of 590 patients documented to have significant obstructive disease by coronary arteriography. Ventriculographic findings, age, history, cigarette smoking, hypertension, serum cholesterol, and diabetes were correlated with prognosis. In categories separated on the basis of left ventricular angiogram the 5-year cardiac mortality rates ranged from 25% among patients with normal left ventricles to 69% among patients with dilated and generally poorly contracting left ventricles. Combining the results of coronary and left ventricular angiography yielded a better prediction than either method separately. Most of the other parameters studied were related to a certain extent to mortality, but their predictive power was limited and could partly or entirely be explained by the associated obstructions of the coronary arteries or the condition of the left ventricle. The most significant clinical determinants were the history, the electrocardiogram, and the presence of diabetes mellitus. Particularly high mortality was found in patients with congestive heart failure or electrocardiographic conduction disturbances.