Cardiopulmonary bypass management and risk of new-onset atrial fibrillation after cardiac surgery.

OBJECTIVES: Cardiopulmonary bypass (CPB) management may potentially play a role in the development of new-onset atrial fibrillation (AF) after cardiac surgery. The aim of this study was to explore this potential association. METHODS: Patients who underwent coronary artery bypass grafting and/or valvular surgery during 2016-2020 were included in an observational single-centre study. Data collected from the Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies registry and a local CPB database were merged. Associations between individual CPB variables (CPB and aortic clamp times, arterial and central venous pressure, mixed venous oxygen saturation, blood flow index, bladder temperature and haematocrit) and new-onset AF were analysed using multivariable logistic regression models adjusted for patient characteristics, comorbidities and surgical procedure. RESULTS: Out of 1999 patients, 758 (37.9%) developed new-onset AF. Patients with new-onset postoperative AF were older, had a higher incidence of previous stroke, worse renal function and higher EuroSCORE II and CHA2DS2-VASc scores and more often underwent valve surgery. Longer CPB time [adjusted odds ratio 1.05 per 10 min (95% confidence interval 1.01-1.08); P = 0.008] and higher flow index [adjusted odds ratio 1.21 per 0.2 l/m2 (95% confidence interval 1.02-1.42); P = 0.026] were associated with an increased risk for new-onset AF, while the other variables were not. A sensitivity analysis only including patients with isolated coronary artery bypass grafting supported the primary analyses. CONCLUSIONS: CPB management following current guideline recommendations appears to have minor or no influence on the risk of developing new-onset AF after cardiac surgery.

Spatiotemporal repolarization dispersion before and after exercise in patients with long QT syndrome type 1 versus controls: probing into the arrhythmia substrate.

Congenital long QT syndrome (LQTS) carries an increased risk for syncope and sudden death. QT prolongation promotes ventricular extrasystoles, which, in the presence of an arrhythmia substrate, might trigger ventricular tachycardia degenerating into fibrillation. Increased electrical heterogeneity (dispersion) is the suggested arrhythmia substrate in LQTS. In the most common subtype LQT1, physical exercise predisposes for arrhythmia and spatiotemporal dispersion was therefore studied in this context. Thirty-seven patients (57% on ß-blockers) and 37 healthy controls (mean age, 31 vs. 35; range, 6-68 vs. 6-72 yr) performed an exercise test. Frank vectorcardiography was used to assess spatiotemporal dispersion as Tampl, Tarea, the ventricular gradient (VG), and the Tpeak-end interval from 10-s signal averages before and 7 ± 2 min after exercise; during exercise too much signal disturbance excluded analysis. Baseline and maximum heart rates as well as estimated exercise intensity were similar, but heart rate recovery was slower in patients. At baseline, QT and heart rate-corrected QT (QTcB) were significantly longer in patients (as expected), whereas dispersion parameters were numerically larger in controls. After exercise, QTpeakcB and Tpeak-endcB increased significantly more in patients (18 ± 23 vs. 7 ± 10 ms and 12 ± 17 vs. 2 ± 6 ms; P < 0.001 and P < 0.01). There was, however, no difference in the change in Tampl, Tarea, and VG between groups. In conclusion, although temporal dispersion of repolarization increased significantly more after exercise in patients with LQT1, there were no signs of exercise-induced increase in global dispersion of action potential duration and morphology. The arrhythmia substrate/mechanism in LQT1 warrants further study.NEW & NOTEWORTHY Physical activity increases the risk for life-threatening arrhythmias in LQTS type 1 (LQT1). The arrhythmia substrate is presumably altered electrical heterogeneity (a.k.a. dispersion). Spatiotemporal dispersion parameters were therefore compared before and after exercise in patients versus healthy controls using Frank vectorcardiography, a novelty. Physical exercise prolonged the time between the earliest and latest complete repolarization in patients versus controls, but did not increase parameters reflecting global dispersion of action potential duration and morphology, another novelty.

Associations between new-onset postoperative atrial fibrillation and long-term outcome in patients undergoing surgical aortic valve replacement.

OBJECTIVES: Data on prognostic implications of new-onset postoperative atrial fibrillation (POAF) after surgical aortic valve replacement (SAVR) is limited. We sought to explore associations between POAF, early initiated oral anticoagulation (OAC) and long-term outcome after SAVR and combined SAVR + coronary artery bypass grafting (CABG). METHODS: This is a retrospective, population-based study including all isolated SAVR (n = 7038) and combined SAVR and CABG patients (n = 3854) without a history of preoperative atrial fibrillation (AF) in Sweden 2007-2017. Individual patient data were merged from 4 nationwide registries. Inverse probability of treatment weighting-adjusted Cox regression models were employed separately in SAVR and SAVR + CABG patients. The median follow-up time was 4.7 years (range 0-10 years). RESULTS: POAF occurred in 44.5% and 50.7% of SAVR and SAVR + CABG patients, respectively. In SAVR patients, POAF was associated with increased long-term risk of death [adjusted hazard ratio (aHR) 1.21 (95% confidence interval 1.06-1.37)], ischaemic stroke [aHR 1.32 (1.08-1.59)], any thromboembolism, heart failure hospitalization and recurrent AF. In SAVR + CABG, POAF was associated with death [aHR 1.31 (1.14-1.51)], recurrent AF and heart failure, but not with ischaemic stroke [aHR 1.04 (0.84-1.29)] or thromboembolism. OAC was dispensed within 30 days after discharge to 67.0% and 65.9%, respectively, of SAVR and SAVR + CABG patients with POAF. Early initiated OAC was not associated with reduced risk of death, ischaemic stroke or thromboembolism in any group of patients. CONCLUSIONS: POAF after SAVR is associated with an increased risk of long-term mortality and morbidity. Further studies are warranted to clarify the role of OAC in SAVR patients with POAF.

Cardiac arrhythmias and conduction abnormalities in patients with type 2 diabetes.

The association between type 2 diabetes (T2D) and the development of cardiac arrhythmias and conduction disturbances has not been extensively studied. Arrhythmia was defined as atrial fibrillation and flutter (AF/AFl), ventricular tachycardia (VT) and ventricular fibrillation (VF), and conduction abnormality as sinus node disease (SND), atrioventricular (AV) block or pacemaker implantation, and intraventricular conduction blocks (IVCB). Incidence rates and Cox regression were used to compare outcomes, and to assess optimal levels for cardiometabolic risk factors and risk associated with multifactorial risk factor control (i.e., HbA1c, LDL-C, systolic blood pressure (SBP), BMI and eGFR), between patients with versus without T2D. The analyses included data from 617,000 patients with T2D and 2,303,391 matched controls. Patients with diabetes and the general population demonstrated a gradual increase in rates for cardiac conduction abnormalities and virtually all age-groups for AF/AFI showed increased incidence during follow-up. For patients with versus without T2D, risks for cardiac arrhythmias were higher, including for AF/AFl (HR 1.17, 95% CI 1.16-1.18), the composite of SND, AV-block or pacemaker implantation (HR 1.40, 95% CI 1.37-1.43), IVCB (HR 1.23, 95% CI 1.18-1.28) and VT/VF (HR 1.08, 95% CI 1.04-1.13). For patients with T2D who had selected cardiometabolic risk factors within target ranges, compared with controls, risk of arrythmia and conduction abnormalities for T2D vs not were: AF/AFl (HR 1.09, 95% CI 1.05-1.14), the composite of SND, AV-block or pacemaker implantation (HR 1.06, 95% CI 0.94-1.18), IVCB (HR 0.80, 95% CI 0.60-0.98), and for VT/VF (HR 0.97, 95% CI 0.80-1.17). Cox models showed a linear risk increase for SBP and BMI, while eGFR showed a U-shaped association. Individuals with T2D had a higher risk of arrhythmias and conduction abnormalities than controls, but excess risk associated with T2D was virtually not evident among patients with T2D with all risk factors within target range. BMI, SBP and eGFR displayed significant associations with outcomes among patients with T2D.

Accelerated QT adaptation following atropine-induced heart rate increase in LQT1 patients versus healthy controls: A sign of disturbed hysteresis.

Hysteresis, a ubiquitous regulatory phenomenon, is a salient feature of the adaptation of ventricular repolarization duration to heart rate (HR) change. We therefore compared the QT interval adaptation to rapid HR increase in patients with the long QT syndrome type 1 (LQT1) versus healthy controls because LQT1 is caused by loss-of-function mutations affecting the repolarizing potassium channel current IKs , presumably an important player in QT hysteresis. The study was performed in an outpatient hospital setting. HR was increased in LQT1 patients and controls by administering an intravenous bolus of atropine (0.04 mg/kg body weight) for 30 s. RR and QT intervals were recorded by continuous Frank vectorcardiography. Atropine induced transient expected side effects but no adverse arrhythmias. There was no difference in HR response (RR intervals) to atropine between the groups. Although atropine-induced ΔQT was 48% greater in 18 LQT1 patients than in 28 controls (p < 0.001), QT adaptation was on average 25% faster in LQT1 patients (measured as the time constant τ for the mono-exponential function and the time for 90% of ΔQT; p < 0.01); however, there was some overlap between the groups, possibly a beta-blocker effect. The shorter QT adaptation time to atropine-induced HR increase in LQT1 patients on the group level corroborates the importance of IKs in QT adaptation hysteresis in humans and shows that LQT1 patients have a disturbed ultra-rapid cardiac memory. On the individual level, the QT adaptation time possibly reflects the effect-size of the loss-of-function mutation, but its clinical implications need to be shown.

Noninvasive electrophysiological differences between women and men: differences in body size not an explanation.

There are numerous sex-related differences in cardiac electrophysiology and arrhythmia propensity but very little knowledge about the reasons. Difference in body size has been proposed as one reason and was tested in this study of >20 cardiac electrophysiology parameters in 319 (158 women) apparently healthy 50- to 64-yr-old subjects from a randomly enrolled population sample, the pilot SCAPIS (Swedish Cardiopulmonary Bioimaging Study), using Frank vectorcardiography. We studied conventional conduction intervals, parameters reflecting electrical heterogeneity (dispersion) in the ventricles, QRS- and T-vector directions, spatial QRS-T angles, and T-vector loop morphology. Body surface area (BSA; 2 methods) and lean body mass (LBM), both estimated from body weight and height, were used as body size parameters. According to multivariable linear regression analysis adjusted for sex, there was no association between electrophysiological parameters and body size apart from QRS duration and QRSarea. In conclusion, most electrophysiological parameters assessed completely noninvasively and showing statistically significant differences between women and men on the group level show no association with BSA or LBM. Scaling (indexing) the electrophysiological parameters for body size parameters is therefore not an option. Consequently, the explanation for the sex-related electrophysiological differences should be sought along other lines.NEW & NOTEWORTHY We sought explanations for sex-related differences in >20 cardiac electrophysiology parameters including conventional conduction intervals in 319 (158 women) apparently healthy 50- to 64-yr-old subjects using Frank vectorcardiography, a novelty. Our hypothesis that body size was partly explanatory for such differences had to be refuted apart from QRS duration and QRSarea. Scaling (indexing) electrophysiological parameters for body size is therefore not an option and explanations for electrophysiological sex-related differences are to be sought elsewhere.

[The AV node - an enigmatic ¼black box« located in the centre of the heart]. / AV-knutan ­ en gåtfull ¼svart låda« med många funktioner.

This commentary refers to a case report describing dual ventricular responses following a single P-wave, which is an unusual but possibly underdiagnosed phenomenon. The AV node synchronizes atrial and ventricular mechanical functions, acts as an electrical filter protecting the ventricles from high heart rates during atrial fibrillation and flutter and is also a back-up generator if the sinus node fails. Dual AV-nodal pathways are the substrate for the relatively common AV-nodal re-entrant tachycardia (AVNRT), which is curable by ablation. Ablation is also the therapy of choice when dual ventricular responses cause palpitations with or without AVNRT, or in rare cases of continuously impaired ventricular mechanical function.

Accessory pathway properties are similar in symptomatic and asymptomatic preexcitation.

PURPOSE: Patients with WPW syndrome have an increased mortality rate compared to the general population. Although asymptomatic preexcitation has previously been considered benign, recent studies have found that also asymptomatic patients have clinical and electrophysiological factors associated with increased risk of sudden cardiac death. This study compares the baseline electrophysiological characteristics of accessory pathways in symptomatic and asymptomatic patients with preexcitation. We hypothesized that a significant proportion of asymptomatic patients has inducible orthodromic tachycardia during programmed electrical stimulation. METHODS: This retrospective study includes 1853 patients with preexcitation who underwent invasive electrophysiological testing in two Swedish University Hospitals between 1991 and 2018. The mean age was 36 ± 17 years with a range of 3-89 years. Thirty-nine percent was women. A total of 269 patients (15%) were children younger than 18 years. Electrophysiological data included effective refractory period of the accessory pathway (APERP, in 1069 patients), tachycardia cycle length, inducibility and type of tachycardia, and AP localization. RESULTS: A total of 1703 (93%) patients reported symptoms suggesting tachyarrhythmias before the study and 128 (7%) were asymptomatic. The proportion of potentially dangerous pathways with short APERP (≤ 250 ms) were similar in symptomatic and asymptomatic patients (187/949, 20% vs. 25/108, 23%) (P = 0.40) as was the mean APERP (303 ± 68 ms vs. 307 ± 75) (P = 0.61). The proportion of patients who had inducible arrhythmia was larger in the symptomatic group (64% vs. 31%) (P < 0.001). CONCLUSION: The results of this study strengthen the present guideline recommendation (IIA) to consider invasive risk assessment in patients with asymptomatic preexcitation.

Stroke Risk Stratification in Patients With Postoperative Atrial Fibrillation After Coronary Artery Bypass Grafting.

Background The CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes, previous stroke or TIA [transient ischemic attack], vascular disease, age 65 to 74 years, sex category female; 2 indicates 2 points, otherwise 1 point) scoring system is recommended to guide decisions on oral anticoagulation therapy for stroke prevention in patients with nonsurgery atrial fibrillation. A score ≥1 in men and ≥2 in women, corresponding to an annual stroke risk exceeding 1%, warrants long-term oral anticoagulation provided the bleeding risk is acceptable. However, in patients with new-onset postoperative atrial fibrillation, the optimal risk stratification method is unknown. The aim of this study was therefore to evaluate the CHA2DS2-VASc scoring system for estimating the 1-year ischemic stroke risk in patients with new-onset postoperative atrial fibrillation after coronary artery bypass grafting. Methods and Results All patients with new-onset postoperative atrial fibrillation and without oral anticoagulation after first-time isolated coronary artery bypass grafting performed in Sweden during 2007 to 2017 were eligible for this registry-based observational cohort study. The 1-year ischemic stroke rate at each step of the CHA2DS2-VASc score was estimated using a Kaplan-Meier estimator. Of the 6368 patients included (mean age, 69.9 years; 81% men), >97% were treated with antiplatelet drugs. There were 147 ischemic strokes during the first year of follow-up. The ischemic stroke rate at 1 year was 0.3%, 0.7%, and 1.5% in patients with CHA2DS2-VASc scores of 1, 2, and 3, respectively, and ≥2.3% in patients with a score ≥4. A sensitivity analysis, with the inclusion of patients on anticoagulants, was performed and supported the primary results. Conclusions Patients with new-onset atrial fibrillation after coronary artery bypass grafting and a CHA2DS2-VASc score <3 have such a low 1-year risk for ischemic stroke that oral anticoagulation therapy should probably be avoided.

Effects of 3 months of detraining following cardiac rehabilitation in patients with atrial fibrillation.

BACKGROUND: Atrial fibrillation negatively impacts physical fitness and health-related quality of life. We recently showed that 3 months of physiotherapist-led exercise-based cardiac rehabilitation improves physical fitness and muscle function in elderly patients with permanent atrial fibrillation and concomitant diseases. Little is, however, known about the consequences for physical fitness, physical activity level, and health-related quality of life after ending the rehabilitation period. METHODS: Prospective 3 months follow-up study of 38 patients out of 40 eligible (10 women) who, as part of a randomized controlled trial, had completed a 3 months physiotherapist-led cardiac rehabilitation resulting in improved physical fitness,. In the current study, the participants were instructed to refrain from exercise for 3 months after completion of the rehabilitation period. Primary outcome measure was physical fitness measured as highest achieved workload using an exercise tolerance test. Secondary outcome measures were muscle function (muscle endurance tests), physical activity level (questionnaire and accelerometer), and health-related quality of life, (Short Form-36), as in the preceding intervention study. We used the Wilcoxon Signed Rank test to analyse differences between the end of rehabilitation and at follow-up. The effect size was determined using Cohen's d . RESULTS: Exercise capacity and exercise time significantly decresead between end of rehabilitation and at follow-up (p < .0001 for both). A significant reduction in shoulder flexion repetitions (p = .006) was observed as well as reduced health-related quality of life in the Short Form-36 dimensions Physical Function (p = .042), Mental Health (p = .030), and Mental Component Score (p = .035). There were, however, no changes regarding objective and subjective physical activity measurements. CONCLUSION: In older patients with permanent atrial fibrillation, previously achieved improvements from physiotherapist-led exercise-based cardiac rehabilitation in physical fitness and muscle function were lost, and health-related quality of life was impaired after ending the rehabilitation period. A strategy for conserving improvements after a rehabilitation period is essential.

Clinical Course of Postoperative Atrial Fibrillation After Cardiac Surgery and Long-term Outcome.

BACKGROUND: New-onset postoperative atrial fibrillation (POAF) after cardiac surgery is associated with worse short- and long-term outcomes. Although the clinical presentation of POAF varies substantially, almost all studies model it with a dichotomous yes or no variable. We explored potential associations between the clinical course of POAF and long-term outcome. METHODS: This retrospective, observational, single-center study included 6435 coronary artery bypass grafting and/or valve patients between 2010 and 2018. POAF patients were grouped into spontaneous/pharmacologic conversion to sinus rhythm, sinus rhythm after electrical cardioversion, and sustained AF at discharge. Multivariable Cox regression models adjusted for age, sex, type of surgery, comorbidities, and early-initiated oral anticoagulation were used to study associations between the clinical course of POAF and long-term risk for mortality, ischemic stroke, thromboembolic events, heart failure hospitalization, and major bleeding. Median follow-up time was 3.8 years (range, 0-8.3). RESULTS: POAF occurred in 2172 patients (33.8%), 94.9% of whom converted to sinus rhythm before discharge. Of these, 73.6% converted spontaneously or with pharmacologic treatment and 26.4% after electrical cardioversion. Both sustained AF and electrical cardioversion were independently associated with an increased long-term risk for heart failure (adjusted hazard ratio for sustained AF at discharge, 2.55 [95% confidence interval, 1.65-3.93; P < .001]; adjusted hazard ratio for electrical cardioversion, 1.28 [95% confidence interval, 1.00-1.65; P = .049]) but not with increased long-term risk for death, thromboembolic complications, or bleeding. CONCLUSIONS: A more complicated POAF course is associated with increased long-term risk for heart failure hospitalization but not for all-cause mortality or thromboembolic complications.

Adaptation of ventricular repolarization dispersion during heart rate increase in humans: A roller coaster process.

BACKGROUND: Regional differences in ventricular activation sequence and action potential duration and morphology result in dispersion in ventricular repolarization (VR). VR dispersion is a key factor in arrhythmogenesis. We studied the adaptation of global VR dispersion in humans during normal and abnormal ventricular activation, and the relation to the QT adaptation (hysteresis). METHODS: We measured global VR dispersion as T amplitude, T area, and ventricular gradient (VG), using continuous Frank vectorcardiography, in response to abrupt and sustained atrial (AP) or ventricular pacing (VP) aiming at 120 bpm, in 21 subjects with permanent pacemakers. RESULTS: Following pacing start, VR adaptation showed an initially rapid and complex tri-phasic pattern, most pronounced for T amplitude. There were major differences in the patterns of VR dispersion adaptation following abrupt AP vs VP, confirming that the adaptation pattern is activation dependent. In response to AP, an instantaneous decrease in VR dispersion occurred, followed by an increase and then a slow decrease, all at a lower level than baseline. In contrast, following VP there was an immediate increase to ~4× baseline in T amplitude and T area (but not in VG), with a subsequent biphasic adaptation lasting longer during VP than AP. The initial rapid changes occurred within the time for QT adaptation to reach steady-state. CONCLUSIONS: Our results corroborate and expand data from animal and invasive human studies, showing similarities of the adaptation pattern on different scales. The initial rapidly changing VR adaptation phase presumably reflects a window of increased vulnerability to arrhythmias.

The results of health-related quality of life assessment depend on the prevailing rhythm at the assessment: Experience from the CAPTAF trial (Catheter Ablation Compared with Pharmacological Therapy for Atrial Fibrillation).

AIMS: To assess whether the prevailing rhythm at the time of replying to symptom and health-related quality of life (HR-QoL) questionnaires impacts the findings. METHOD: A total of 150 patients from the randomized Catheter Ablation Compared with Pharmacological Therapy for Atrial Fibrillation-trial, comparing atrial fibrillation (AF) ablation versus drugs, were included. The effect of the prevailing rhythm on the outcome results of the HR-QoL 36-Item Short-Form Health Survey, the symptom severity questionnaire (SSQ), and the European Heart Rhythm Association (EHRA) score for classification of AF-related symptoms was assessed. RESULTS: AF as the prevailing rhythm was independently associated with a significantly lower Vitality score; 18.4 points lower (95% confidence interval -32.7 to -4.1, p = .01) compared with sinus rhythm when adjusted for AF burden, median duration of episode, number of episodes, beta-blocker use, type of AF, and sex. The presence of AF did not affect the General Health score compared with sinus rhythm, nor did it influence symptoms assessed by the SSQ or EHRA score. CONCLUSION: The observation that the presence of AF versus sinus rhythm when conducting HR-QoL tests had a negative impact on its outcome, leaving symptom-related questionnaires unaffected, implies that the prevailing rhythm should be taken into account when results of HR-QoL questionnaires are interpreted.

Atrial fibrillation burden, episode duration and frequency in relation to quality of life in patients with implantable cardiac monitor.

AIMS: To assess the relation between atrial fibrillation (AF) characteristics and health-related quality of life (QoL), and which AF characteristic had the greatest impact. METHOD: The AF characteristics burden (percentage of time in AF), duration and number of AF episodes/month were obtained from implantable cardiac monitors during the 2-month run-in period in 150 patients included in the randomized CAPTAF trial comparing early ablation and antiarrhythmic drug therapy. The QoL was measured by the General Health and Vitality dimensions of the 36-Item Short-Form Health Survey. AF characteristics were analysed continuously and in quartiles (Q1-Q4). RESULTS: Greater AF burden (p = 0.003) and longer AF episodes (p = 0.013) were associated with impaired QoL (Vitality score only) in simple linear regression analyses. Greater AF burden was, however, the only AF characteristic associated with lower QoL, when adjusted for sex, type of AF, hypertension, heart rate above 110 beats per minute during AF, and beta-blocker use in multiple linear regression analyses. For every 10% increase in AF burden there was a 1.34-point decrease of Vitality score (95% confidence interval (CI) -2.67 to -0.02, p = 0.047). The Vitality score was 12 points lower (95% CI -22.73 to -1.27, p = 0.03) in patients with an AF burden > 33% (Q4) versus those with < 0.45% (Q1), but only in unadjusted analysis. CONCLUSION: AF burden had a greater impact on QoL (Vitality), than the duration and number of AF episodes, corroborating that AF burden may be the preferred outcome measure of rhythm control in trials including relatively healthy AF populations.

New-Onset Atrial Fibrillation After Coronary Artery Bypass Grafting and Long-Term Outcome: A Population-Based Nationwide Study From the SWEDEHEART Registry.

Background The long-term impact of new-onset postoperative atrial fibrillation (POAF) after coronary artery bypass grafting and the benefit of early-initiated oral anticoagulation (OAC) in patients with POAF are uncertain. Methods and Results All patients who underwent coronary artery bypass grafting without preoperative atrial fibrillation in Sweden from 2007 to 2015 were included in a population-based study using data from 4 national registries: SWEDEHEART (Swedish Web System for Enhancement and Development of Evidence-based Care in Heart Disease Evaluated According to Recommended Therapies), National Patient Registry, Dispensed Drug Registry, and Cause of Death Registry. POAF was defined as any new-onset atrial fibrillation during the first 30 postoperative days. Cox regression models (adjusted for age, sex, comorbidity, and medication) were used to assess long-term outcome in patients with and without POAF, and potential associations between early-initiated OAC and outcome. In a cohort of 24 523 patients with coronary artery bypass grafting, POAF occurred in 7368 patients (30.0%), and 1770 (24.0%) of them were prescribed OAC within 30 days after surgery. During follow-up (median 4.5 years, range 0‒9 years), POAF was associated with increased risk of ischemic stroke (adjusted hazard ratio [aHR] 1.18 [95% CI, 1.05‒1.32]), any thromboembolism (ischemic stroke, transient ischemic attack, or peripheral arterial embolism) (aHR 1.16, 1.05‒1.28), heart failure hospitalization (aHR 1.35, 1.21‒1.51), and recurrent atrial fibrillation (aHR 4.16, 3.76‒4.60), but not with all-cause mortality (aHR 1.08, 0.98‒1.18). Early initiation of OAC was not associated with reduced risk of ischemic stroke or any thromboembolism but with increased risk for major bleeding (aHR 1.40, 1.08‒1.82). Conclusions POAF after coronary artery bypass grafting is associated with negative prognostic impact. The role of early OAC therapy remains unclear. Studies aiming at reducing the occurrence of POAF and its consequences are warranted.

Adaptation of ventricular repolarization time following abrupt changes in heart rate: comparisons and reproducibility of repeated atrial and ventricular pacing.

Adequate adaptation of ventricular repolarization (VR) duration to changes in heart rate (HR) is important for cardiac electromechanical function and electrical stability. We studied the QT and QTpeak adaptation in response to abrupt start and stop of atrial and ventricular pacing on two occasions with an interval of at least 1 mo in 25 study subjects with permanent pacemakers. Frank vectorcardiography was used for data collection. Atrial or ventricular pacing was performed for 8 min aiming at a cycle length (CL) of 500 ms. We measured the immediate response (IR), the time constant (τ) of the exponential phase, and T90 End, the time to reach 90% change of QT and QTpeak from baseline to steady state during and after pacing. During atrial pacing, the CL decreased on average 45% from mean (SD) 944 (120) to 518 (46) ms and QT decreased on average 18% from 388 (20) to 318 (17) ms. For QT, T90 End was 103 (24) s and 126 (15) s after start versus stop of atrial pacing; a difference of 24 (27) s (P = 0.006). The response pattern was similar for τ but IR did not differ significantly between pacing start and stop. The response pattern was similar for QTpeak and also for QT and QTpeak following ventricular pacing start and stop. The coefficients of variation for repeated measures were 7%-21% for T90 End and τ. In conclusion, the adaptation of VR duration was significantly more rapid following increasing than decreasing HR and intraindividually a relatively reproducible process.NEW & NOTEWORTHY We studied the duration of ventricular repolarization (VR) adaptation and its hysteresis, following increasing and decreasing heart rate by abrupt start and stop of 8-min atrial or ventricular pacing in study subjects with permanent pacemakers and repeated the protocol with ≥1 mo interval, a novel approach. VR adaptation was significantly longer following decreasing than increasing heart rate corroborating previous observations. Furthermore, VR adaptation was intraindividually a reproducible and, hence, robust phenomenon, a novel finding.

QT correction using Bazett's formula remains preferable in long QT syndrome type 1 and 2.

BACKGROUND: The heart rate (HR) corrected QT interval (QTc) is crucial for diagnosis and risk stratification in the long QT syndrome (LQTS). Although its use has been questioned in some contexts, Bazett's formula has been applied in most diagnostic and prognostic studies in LQTS patients. However, studies on which formula eliminates the inverse relation between QT and HR are lacking in LQTS patients. We therefore determined which QT correction formula is most appropriate in LQTS patients including the effect of beta blocker therapy and an evaluation of the agreement of the formulae when applying specific QTc limits for diagnostic and prognostic purposes. METHODS: Automated measurements from routine 12-lead ECGs from 200 genetically confirmed LQTS patients from two Swedish regions were included (167 LQT1, 33 LQT2). QT correction was performed using the Bazett, Framingham, Fridericia, and Hodges formulae. Linear regression was used to compare the formulae in all patients, and before and after the initiation of beta blocking therapy in a subgroup (n = 44). Concordance analysis was performed for QTc ≥ 480 ms (diagnosis) and ≥500 ms (prognosis). RESULTS: The median age was 32 years (range 0.1-78), 123 (62%) were female and 52 (26%) were children ≤16 years. Bazett's formula was the only method resulting in a QTc without relation with HR. Initiation of beta blocking therapy did not alter the result. Concordance analyses showed clinically significant differences (Cohen's kappa 0.629-0.469) for diagnosis and prognosis in individual patients. CONCLUSION: Bazett's formula remains preferable for diagnosis and prognosis in LQT1 and 2 patients.

Automatic identification of a stable QRST complex for non-invasive evaluation of human cardiac electrophysiology.

BACKGROUND: A vectorcardiography approach to electrocardiology contributes to the non-invasive assessment of electrical heterogeneity in the ventricles of the heart and to risk stratification for cardiac events including sudden cardiac death. The aim of this study was to develop an automatic method that identifies a representative QRST complex (QRSonset to Tend) from a Frank vectorcardiogram (VCG). This method should provide reliable measurements of morphological VCG parameters and signal when such measurements required manual scrutiny. METHODS: Frank VCG was recorded in a population-based sample of 1094 participants (550 women) 50-65 years old as part of the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot. Standardized supine rest allowing heart rate stabilization and adaptation of ventricular repolarization preceded a recording period lasting ≥5 minutes. In the Frank VCG a recording segment during steady-state conditions and with good signal quality was selected based on QRST variability. In this segment a representative signal-averaged QRST complex from cardiac cycles during 10s was selected. Twenty-eight morphological parameters were calculated including both conventional conduction intervals and VCG-derived parameters. The reliability and reproducibility of these parameters were evaluated when using completely automatic and automatic but manually edited annotation points. RESULTS: In 1080 participants (98.7%) our automatic method reliably selected a representative QRST complex where its instability measure effectively identified signal variability due to both external disturbances ("noise") and physiologic and pathophysiologic variability, such as e.g. sinus arrhythmia and atrial fibrillation. There were significant sex-related differences in 24 of 28 VCG parameters. Some VCG parameters were insensitive to the instability value, while others were moderately sensitive. CONCLUSION: We developed an automatic process for identification of a signal-averaged QRST complex suitable for morphologic measurements which worked reliably in 99% of participants. This process is applicable for all non-invasive analyses of cardiac electrophysiology including risk stratification for cardiac death based on such measurements.