Lone atrial fibrillation: where are we now?

Diagnostic Efficacy of Cardiac Scintigraphy with 99mTc-Pyrophosphate for Latent Myocardial Inflammation in Patients with Atrial Fibrillation

Objectives

This work aimed to study the efficacy of hybrid ^99mTc-Pyrophosphate SPECT/CT for diagnosis of latent inflammatory processes in the myocardium of patients with atrial fibrillation (AF).

Methods

The study comprised 34 patients aged 44 ± 9 years with AF of unknown etiology referred for radiofrequency ablation. The data were acquired using hybrid ^99mTc-Pyrophosphate SPECT/CT. To evaluate and interpret the results of hybrid study and to determine localization of radiopharmaceutical accumulation, scintigraphic and CT images were fused. SPECT/CT results were compared with data of endomyocardial biopsy.

Results

Sensitivity, specificity, and accuracy of ^99mTc-Pyrophosphate SPECT/CT in diagnosing myocarditis were 91%, 100%, and 94%, respectively. Proposed diagnostic criteria for myocarditis comprised intensity of the radiopharmaceutical accumulation in the myocardium and the ratios of focus/lung, focus/vertebral column, and focus/LV pool. Minimum cutoff values for the histologically verified myocarditis were >1.47 for focus/lung index, >0.11 for focus/vertebral column ratio, and >1.26 for focus/lung index.

Conclusions

SPECT/CT-based quantitative assessment of ^99mTc-Pyrophosphate accumulation in the myocardium is a highly informative noninvasive method for diagnosis of inflammatory process in the heart in patients with AF of undefined etiology.

Atrial fibrillation without comorbidities: Prevalence, incidence and prognosis (from the Framingham Heart Study)

BACKGROUND

The epidemiology of atrial fibrillation (AF) without comorbidities, known as 'lone AF', is uncertain. Although it has been considered a benign condition, we hypothesized that it confers a worse prognosis compared with a matched sample without AF.

METHODS

We described the proportion of AF without comorbidities (clinical, subclinical cardiovascular disease and triggers) among the entire AF sample in Framingham Heart Study (FHS). We compared AF without comorbidities with typical AF, and age-, sex- and cohort-matched individuals without AF, using Cox proportional hazards analysis in relation to combined cardiovascular events (stroke, heart failure, myocardial infarction), and mortality.

RESULTS

Of 10,311 FHS participants, 1,961 were diagnosed with incident AF, among which 173 individuals had AF without comorbidities (47% women, mean age 71±12 years). AF without comorbidities had a prevalence of 1.7% of the entire cohort, and an annual incidence of 0.5 per 1000 person-years. During a median follow-up of 9.7 years after initial AF, 137 individuals with AF without comorbidities (79.2%) died and 141 individuals developed cardiovascular events (81.5%). AF without comorbidities had significantly lower mortality (HR 0.67, 95%CI 0.55-0.81, P < .001) and total cardiovascular events (HR 0.66, 95% CI 0.55-0.80, P < .001) compared with typical AF. However, mortality (HR1.43, 95% CI 1.18-1.75, P < .001) and risk of total cardiovascular events (HR 1.73, 95% CI 1.39-2.16, P < .001) were higher than age-, sex-, and cohort-matched individuals without AF.

CONCLUSIONS

The risk of cardiovascular outcomes and mortality among individuals with AF without comorbidities is lower than typical AF, but is significantly elevated compared with matched individuals without AF.

Inflammation, oxidative stress and postoperative atrial fibrillation in cardiac surgery

Postoperative atrial fibrillation (POAF) is a common complication of cardiac surgery that occurs in up to 60% of patients. POAF is associated with increased risk of cardiovascular mortality, stroke and other arrhythmias that can impact on early and long term clinical outcomes and health economics. Many factors such as disease-induced cardiac remodelling, operative trauma, changes in atrial pressure and chemical stimulation and reflex sympathetic/parasympathetic activation have been implicated in the development of POAF. There is mounting evidence to support a major role for inflammation and oxidative stress in the pathogenesis of POAF. Both are consequences of using cardiopulmonary bypass and reperfusion following ischaemic cardioplegic arrest. Subsequently, several anti-inflammatory and antioxidant drugs have been tested in an attempt to reduce the incidence of POAF. However, prevention remains suboptimal and thus far none of the tested drugs has provided sufficient efficacy to be widely introduced in clinical practice. A better understanding of the cellular and molecular mechanisms responsible for the onset and persistence of POAF is needed to develop more effective prediction and interventions.

Lone atrial fibrillation - an overview

Atrial fibrillation (AF) sometimes develops in younger individuals without any evident cardiac or other disease. To refer to these patients who were considered to have a very favourable prognosis compared with other AF patients, the term 'lone' AF was introduced in 1953. However, there are numerous uncertainties associated with 'lone' AF, including inconsistent entity definitions, considerable variations in the reported prevalence and outcomes, etc. Indeed, increasing evidence suggests a number of often subtle cardiac alterations associated with apparently 'lone' AF, which may have relevant prognostic implications. Hence, 'lone' AF patients comprise a rather heterogeneous cohort, and may have largely variable risk profiles based on the presence (or absence) of overlooked subclinical cardiovascular risk factors or genetically determined subtle alterations at the cellular or molecular level. Whether the implementation of various cardiac imaging techniques, biomarkers and genetic information could improve the prediction of risk for incident AF and risk assessment of 'lone' AF patients, and influence the treatment decisions needs further research. In this review, we summarise the current knowledge on 'lone' AF, highlight the existing inconsistencies in the field and discuss the prognostic and treatment implications of recent insights in 'lone' AF pathophysiology.

[Atrial fibrillation and physical activity]

Atrial fibrillation is the most frequent arrhythmia. Its "lone" form (when underlying pathology is not discovered) can be detected in a small percentage of endurance sports participants, and in growing numbers among veterans, probably as a result of some cardiac or other irregularities. Enhanced vagal tone and sudden sympathetic impulse, repetitive oxidative stress, inflammatory processes, enlarged atria, electric instabilization can explain the higher occurrence. Treatment of atrial fibrillation enables the affected persons to participate in regular medium-intensity exercise, 3-5 hours a week, which offers a protective role against cardiovascular, metabolic and mental illnesses.

Clinically unrecognized mitral regurgitation is prevalent in lone atrial fibrillation

AIM

To investigate the prevalence of clinically unrecognized mitral regurgitation (MR) in lone atrial fibrillation (AF).

METHODS

We studied the prevalence and severity of MR by transesophageal echocardiography (TEE) in patients with "lone" AF as compared to a matched cohort of patients in normal sinus rhythm (NSR) undergoing TEE for other indications besides recognized valvular heart disease.

RESULTS

A total of 157 subjects (57 in the AF group and 100 in the NSR group) with structurally normal cardiac valves were included in the study. In the AF group, moderate MR or more was noted in 66% of the patients, mild MR in 18%, trace or no MR in 16%. In the control group, moderate MR was noted in 6% of patients, mild MR 31%, trace or no MR in 63 % of patients. Moderate MR or greater was significantly more prevalent in the AF group compared to the NSR group (66% vs 6%, P < 0.0001).

CONCLUSION

Clinically unrecognized moderate MR is prevalent in "lone" AF -either as an etiologic factor leading to "lone" AF or developing after onset of AF.