P-wave morphology is unaffected by atrial size: a study in healthy athletes

Atrial cardiomyopathy markers predict ischemic cerebrovascular events independent of atrial fibrillation in patients with acute myocardial infarction

Background

Contemporary data on atrial cardiomyopathy (ACM) markers and ischemic cerebrovascular events (ICVE) in patients with acute myocardial infarction (AMI) is lacking. We aimed to examine whether ACM markers predict ICVE among AMI patients.

Materials and methods

A total of 4,206 AMI cases diagnosed in clinical examinations between January 2016 and June 2021 were assessed for markers of ACM including B-type natriuretic peptide (BNP), P-wave terminal force in ECG lead V1 (PTFV1), and left atrium diameter (LAD). Left atrial enlargement (LAE) and abnormal PTFV1 were defined by previously published cut-off points. The primary outcome was incident ICVE composed of ischemic stroke (IS) and transient ischemic attack (TIA). Receiver operating curve analyses were used to compare the predictive performance of the CHA2DS2-VASc score combined with ACM markers to the CHA2DS2-VASc score alone.

Results

During a median follow-up of 44.0 months, 229 (5.44%) ICVE occurred. Of these, 156 individuals developed IS and the remaining 73 cases were diagnosed with TIAs. The ICVE group showed larger PTFV1 and increased LAD as well as elevated BNP levels at baseline. In the multivariate analysis, we found significant associations with ICVE for PTFV1 (HR per 1,000 μV*ms, 1.143; 95% CI, 1.093–1.196), LAD (HR per millimeter, 1.148; 95% CI, 1.107–1.190), but not BNP after adjusting for known ICVE risk factors and interim atrial fibrillation (AF). The addition of abnormal PTFV1 and LAE improved the predictive accuracy of the CHA2DS2-VASc score with C-statistic increasing from 0.708 to 0.761 (p < 0.001).

Conclusion

Atrial cardiomyopathy markers including PTFV1 and LAD were associated with incident ICVE independent of well-established risk factors and AF occurrence. The addition of ACM markers with CHA2DS2-VASc score may well discriminate individuals at high risk of ICVE in AMI patients.

Atrial cardiomyopathy: from cell to bedside

Atrial cardiomyopathy refers to structural and electrical remodelling of the atria, which can lead to impaired mechanical function. While historical studies have implicated atrial fibrillation as the leading cause of cardioembolic stroke, atrial cardiomyopathy may be an important, underestimated contributor. To date, the relationship between atrial cardiomyopathy, atrial fibrillation, and cardioembolic stroke remains obscure. This review summarizes the pathogenesis of atrial cardiomyopathy, with a special focus on neurohormonal and inflammatory mechanisms, as well as the role of adipose tissue, especially epicardial fat in atrial remodelling. It reviews the current evidence implicating atrial cardiomyopathy as a cause of embolic stroke, with atrial fibrillation as a lagging marker of an increased thrombogenic atrial substrate. Finally, it discusses the potential of antithrombotic therapy in embolic stroke with undetermined source and appraises the available diagnostic techniques for atrial cardiomyopathy, including imaging techniques such as echocardiography, computed tomography, and magnetic resonance imaging as well as electroanatomic mapping, electrocardiogram, biomarkers, and genetic testing. More prospective studies are needed to define the relationship between atrial cardiomyopathy, atrial fibrillation, and embolic stroke and to establish a prompt diagnosis and specific treatment strategies in these patients with atrial cardiomyopathy for the secondary and even primary prevention of embolic stroke.

Central Sleep Apnea Is Associated with an Abnormal P-Wave Terminal Force in Lead V1 in Patients with Acute Myocardial Infarction Independent from Ventricular Function

Sleep-disordered breathing (SDB) is highly prevalent in patients with cardiovascular disease. We have recently shown that an elevation of the electrocardiographic (ECG) parameter P wave terminal force in lead V₁ (PTFV₁) is linked to atrial proarrhythmic activity by stimulation of reactive oxygen species (ROS)-dependent pathways. Since SDB leads to increased ROS generation, we aimed to investigate the relationship between SDB-related hypoxia and PTFV₁ in patients with first-time acute myocardial infarction (AMI). We examined 56 patients with first-time AMI. PTFV₁ was analyzed in 12-lead ECGs and defined as abnormal when ≥4000 µV*ms. Polysomnography (PSG) to assess SDB was performed within 3–5 days after AMI. SDB was defined by an apnea-hypopnea-index (AHI) >15/h. The multivariable regression analysis showed a significant association between SDB-related hypoxia and the magnitude of PTFV₁ independent from other relevant clinical co-factors. Interestingly, this association was mainly driven by central but not obstructive apnea events. Additionally, abnormal PTFV₁ was associated with SDB severity (as measured by AHI, B 21.495; CI [10.872 to 32.118]; p < 0.001), suggesting that ECG may help identify patients suitable for SDB screening. Hypoxia as a consequence of central sleep apnea may result in atrial electrical remodeling measured by abnormal PTFV₁ in patients with first-time AMI independent of ventricular function. The PTFV₁ may be used as a clinical marker for increased SDB risk in cardiovascular patients.

Abnormal P-wave terminal force in lead V1 is a marker for atrial electrical dysfunction but not structural remodelling

Aims

There is a lack of diagnostic and therapeutic options for patients with atrial cardiomyopathy and paroxysmal atrial fibrillation. Interestingly, an abnormal P‐wave terminal force in electrocardiogram lead V₁ (PTFV₁) has been associated with atrial cardiomyopathy, but this association is poorly understood. We investigated PTFV₁ as a marker for functional, electrical, and structural atrial remodelling.

Methods and results

Fifty‐six patients with acute myocardial infarction and 13 kidney donors as control cohort prospectively underwent cardiac magnetic resonance imaging to evaluate the association between PTFV₁ and functional remodelling (atrial strain). To further investigate underlying pathomechanisms, right atrial appendage biopsies were collected from 32 patients undergoing elective coronary artery bypass grafting. PTFV₁ was assessed as the product of negative P‐wave amplitude and duration in lead V₁ and defined as abnormal if ≥4000 ms*μV. Activity of cardiac Ca/calmodulin‐dependent protein kinase II (CaMKII) was determined by a specific HDAC4 pull‐down assay as a surrogate for electrical remodelling. Atrial fibrosis was quantified using Masson's trichrome staining as a measure for structural remodelling. Multivariate regression analyses were performed to account for potential confounders. A total of 16/56 (29%) of patients with acute myocardial infarction, 3/13 (23%) of kidney donors, and 15/32 (47%) of patients undergoing coronary artery bypass grafting showed an abnormal PTFV₁. In patients with acute myocardial infarction, left atrial (LA) strain was significantly reduced in the subgroup with an abnormal PTFV₁ (LA reservoir strain: 32.28 ± 12.86% vs. 22.75 ± 13.94%, P = 0.018; LA conduit strain: 18.87 ± 10.34% vs. 10.17 ± 8.26%, P = 0.004). Abnormal PTFV₁ showed a negative correlation with LA conduit strain independent from clinical covariates (coefficient B: −7.336, 95% confidence interval −13.577 to −1.095, P = 0.022). CaMKII activity was significantly increased from (normalized to CaMKII expression) 0.87 ± 0.17 to 1.46 ± 0.15 in patients with an abnormal PTFV₁ (P = 0.047). This increase in patients with an abnormal PTFV₁ was independent from clinical covariates (coefficient B: 0.542, 95% confidence interval 0.057 to 1.027, P = 0.031). Atrial fibrosis was significantly lower with 12.32 ± 1.63% in patients with an abnormal PTFV₁ (vs. 20.50 ± 2.09%, P = 0.006), suggesting PTFV₁ to be a marker for electrical but not structural remodelling.

Conclusions

Abnormal PTFV₁ is an independent predictor for impaired atrial function and for electrical but not for structural remodelling. PTFV₁ may be a promising tool to evaluate patients for atrial cardiomyopathy and for risk of atrial fibrillation.

Usefulness of Electrocardiographic Left Atrial Abnormality to Predict Response to Cardiac Resynchronization Therapy in Patients With Mild Heart Failure and Left Bundle Branch Block (a Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy Substudy)

Cardiac resynchronization therapy (CRT) has proven prognostic benefits in patients with heart failure (HF) with left bundle branch block (LBBB) QRS morphology. Electrocardiographic left atrial (LA) abnormality has been proposed as a noninvasive marker of atrial remodeling. We aimed to assess the impact of electrocardiographic LA abnormality for prognosis in patients with HF treated with CRT. Baseline resting 12-lead electrocardiograms recorded from 941 patients enrolled in the CRT arm of the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy was processed automatically using Glasgow algorithm, which included automated assessment of P-wave terminal force in lead V₁ (PTF-V₁) as a marker of LA abnormality. A PTF-V₁ of ≥0.04 mm⋅s was considered abnormal. The primary end point was HF event and/or death. Total mortality and appropriate defibrillator therapies were the secondary end points. At baseline 550, patients treated with CRT with a defibrillator had LBBB QRS morphology and normal PTF-V₁. Normal PTF-V₁ was associated with significant risk reduction for all assessed end points and for the primary end point comprised a hazard ratio of 0.55 (95% confidence interval 0.36 to 0.84) compared with patients with LBBB with abnormal PTF-V₁ (n = 120), and a hazard ratio of 0.42 (95% confidence interval 0.32 to 0.55) compared with patients with implanted defibrillator (n = 729). In CRT-treated patients with HF, electrocardiographic LA abnormality appears to be an electrocardiographic indicator of poor long-term outcome in patients with LBBB. In conclusion, our data suggest that PTF-V₁ bears additive prognostic information in the context of CRT, thus further strengthening the role of electrocardiographic diagnostics in risk stratification of patients with HF.

Mechanisms of atrial fibrillation in athletes: what we know and what we do not know

Exercise is an emerging cause of atrial fibrillation (AF) in young individuals without coexisting cardiovascular risk factors. The causes of exercise-induced atrial fibrillation remain largely unknown, and conclusions are jeopardised by apparently conflicting data. Some components of the athlete's heart are known to be arrhythmogenic in other settings. Bradycardia, atrial dilatation and, possibly, atrial premature beats are therefore biologically plausible contributors to exercise-induced AF. Challenging findings in an animal model suggest that exercise might also prompt the development of atrial fibrosis, possibly due to cumulative minor structural damage after each exercise bout. However, there is very limited, indirect data supporting this hypothesis in athletes. Age, sex, the presence of comorbidities and cardiovascular risk factors, and genetic individual variability might serve to flag those athletes who are at the higher risk of exercise-induced AF. In this review, we will critically address current knowledge on the mechanisms of exercise-induced AF.

Fifteen Genetic Loci Associated With the Electrocardiographic P Wave

BACKGROUND

The P wave on an ECG is a measure of atrial electric function, and its characteristics may serve as predictors for atrial arrhythmias. Increased mean P-wave duration and P-wave terminal force traditionally have been used as markers for left atrial enlargement, and both have been associated with increased risk of atrial fibrillation. Here, we explore the genetic basis of P-wave morphology through meta-analysis of genome-wide association study results for P-wave duration and P-wave terminal force from 12 cohort studies.

METHODS AND RESULTS

We included 44 456 individuals, of which 6778 (16%) were of African ancestry. Genotyping, imputation, and genome-wide association study were performed at each study site. Summary-level results were meta-analyzed centrally using inverse-variance weighting. In meta-analyses of P-wave duration, we identified 6 significant (P<5×10^-8) novel loci and replicated a prior association with SCN10A. We identified 3 loci at SCN5A, TBX5, and CAV1/CAV2 that were jointly associated with the PR interval, PR segment, and P-wave duration. We identified 6 novel loci in meta-analysis of P-wave terminal force. Four of the identified genetic loci were significantly associated with gene expression in 329 left atrial samples. Finally, we observed that some of the loci associated with the P wave were linked to overall atrial conduction, whereas others identified distinct phases of atrial conduction.

CONCLUSIONS

We have identified 6 novel genetic loci associated with P-wave duration and 6 novel loci associated with P-wave terminal force. Future studies of these loci may aid in identifying new targets for drugs that may modify atrial conduction or treat atrial arrhythmias.

Orthogonal P-wave morphology is affected by intra-atrial pressures

BACKGROUND

It has previously been shown that the morphology of the P-wave neither depends on atrial size in healthy subjects with physiologically enlarged atria nor on the physiological anatomical variation in transverse orientation of the left atrium. The present study aimed to investigate if different pressures in the left and right atrium are associated with different P-wave morphologies.

METHODS

38 patients with isolated, increased left atrial pressure, 51 patients with isolated, increased right atrial pressure and 76 patients with biatrially increased pressure were studied. All had undergone right heart catheterization and had 12-lead electrocardiographic recordings, which were transformed into vectorcardiograms for detailed P-wave morphology analysis.

RESULTS

Normal P-wave morphology (type 1) was more common in patients with isolated increased pressure in the right atrium while abnormal P-wave morphology (type 2) was more common in the groups with increased left atrial pressure (P = 0.032). Moreover, patients with increased left atrial pressure, either isolated or in conjunction with increased right atrial pressure, had significantly more often a P-wave morphology with a positive deflection in the sagittal plane (P = 0.004).

CONCLUSION

Isolated elevated right atrial pressure was associated with normal P-wave morphology while left-sided atrial pressure elevation, either isolated or in combination with right atrial pressure elevation, was associated with abnormal P-wave morphology.

Physiological variation in left atrial transverse orientation does not influence orthogonal P-wave morphology

BACKGROUND

It has previously been demonstrated that orthogonal P-wave morphology in healthy athletes does not depend on atrial size, but the possible impact of left atrial orientation on P-wave morphology remains unknown. In this study, we investigated if left atrial transverse orientation affects P-wave morphology in different populations.

METHODS

Forty-seven patients with atrial fibrillation, 21 patients with arrhythmogenic right ventricular cardiomyopathy, 67 healthy athletes, and 56 healthy volunteers were included. All underwent cardiac magnetic resonance imaging or computed tomography and the orientation of the left atrium was determined. All had 12-lead electrocardiographic recordings, which were transformed into orthogonal leads and orthogonal P-wave morphology was obtained.

RESULTS

The median left atrial transverse orientation was 87 (83, 91) degrees (lower and upper quartiles) in the total study population. There was no difference in left atrial transverse orientation between individuals with different orthogonal P-wave morphologies.

CONCLUSIONS

The physiological variation in left atrial orientation was small within as well as between the different populations. There was no difference in left atrial transverse orientation between subjects with type 1 and type 2 P-wave morphology, implying that in this setting the P-wave morphology was more dependent on atrial conduction than orientation.