The heart rate response to the 6-min walk test in atrial fibrillation patients with or without beta-blockers: Referring to patients with sinus rhythm

BACKGROUND

The aim was to evaluate the effect of beta-blockers (BB) on the response of heart rate (HR) to 6-min walk test (6MWT) in atrial fibrillation (AF) and whether the AF patients treated with BB have a similar HR response to 6MWT as the AF and sinus rhythm (SR) patients without BB treatment at the same resting HR level.

METHODS

The before-after study involving 74 AF patients was to evaluate the effect of BB treatment (pre-BB and with BB). The comparison study included 74 BB-treated AF patients (with BB), 74 matched AF patients without BB (no BB), and 74 SR patients. The percentage increase amplitude of HR (HR-PIA) in 6MWT was calculated: [(the exercise HR - the resting HR)/(the resting HR)] × 100%.

RESULTS

The before-after study showed that BB treatment decreased the resting and mean exercise HR (98.6 ± 15.2 vs. 85.5 ± 11.2 bpm and 121.3 ± 17.3 vs. 109.0 ± 16.7 bpm) during 6MWT. The comparison study demonstrated that against the SR, the AF with BB and no BB groups have higher mean exercise HR-PIA (28.2 ± 17.1% and 22.0 ± 9.6%, vs. 6.9 ± 3.7%) when their resting HR is similar. Moreover, the mean exercise HR-PIA was also significantly higher in the with BB group than in the no BB group.

CONCLUSION

In AF patients with relatively higher resting HR, BB treatment could decrease the resting and exercise HR during 6MWT. However, BB treatment could not effectively attenuate the exercise HR rise as compared with AF without BB treatment, even with similar resting HR levels.

What about chronotropic incompetence in heart failure with mildly reduced ejection fraction? Clinical and prognostic implications from the Metabolic Exercise combined with Cardiac and Kidney Indexes score dataset

AIMS

Chronotropic incompetence (CI) is a strong predictor of outcome in heart failure with reduced ejection fraction, however no data on its clinical and prognostic impacts in heart failure with mildly reduced ejection fraction (HFmrEF) are available. Therefore, the study aims to investigate, in a large multicentre HFmrEF cohort, the prevalence of CI as well as its relationship with exercise capacity and its prognostic role over the cardiopulmonary exercise testing (CPET) parameters.

METHODS AND RESULTS

Within the Metabolic Exercise combined with Cardiac and Kidney Indexes (MECKI) database, we analysed data of 864 HFmrEF out of 1164 stable outpatients who performed a maximal CPET at the cycle ergometer and who had no significant rhythm disorders or comorbidities. The primary study endpoint was cardiovascular (CV) death. All-cause death was also explored. Chronotropic incompetence prevalence differed depending on the method (peak heart rate, pHR% vs. pHR reserve, pHRR%) and the cut-off adopted (pHR% from ≤75% to ≤60% and pHRR% ≤ 65% to ≤50%), ranging from 11% to 62%. A total of 84 (9.7%) CV deaths were collected, with 39 (4.5%) occurring within 5 years. At multivariate analysis, both pHR% [hazard ratio 0.97 (0.95-0.99), P < 0.05] and pHRR% [hazard ratio 0.977 (0.961-0.993), P < 0.01] were associated with the primary endpoint. A pHR% ≤ 75% and a pHRR% ≤ 50% represented the most accurate cut-off values in predicting the outcome.

CONCLUSION

The study suggests an association between blunted exercise-HR response, functional capacity, and CV death risk among patients with HFmrEF. Whether the CI presence might be adopted in daily HFmrEF management needs to be addressed in larger prospective studies.

Prediction of atrioventricular conduction disturbance after ablation of persistent atrial fibrillation

The prevalence of atrioventricular conduction disturbance (AVCD) in patients with persistent atrial fibrillation (AF) has not yet been fully investigated. We sought to identify the predictors of AVCD in patients with AF by analyzing the relationship between pre-ablation heart rate during AF and the PR interval in sinus rhythm after ablation. We analyzed pre-ablation 24-h Holter electrocardiogram (ECG) and 12 lead ECG 12 months after ablation of 121 consecutive patients with persistent AF who underwent their first ablation procedure and maintained sinus rhythm at 12 months. AVCD was defined as a first-degree atrioventricular block (AVB), second-degree AVB, high-degree AVB, or third-degree AVB observed on ECG at 12 months after ablation. Seventeen out of 121 patients (14.0%) had AVCD at 12 months. In the group with AVCD, total heartbeat (THB) and maximum heart rate (Max HR) were significantly lower, and the prevalence of concomitant Cavo-tricuspid isthmus-dependent atrial flutter before ablation and the appearance of macro reentrant atrial tachycardia (AT) during the procedure were significantly higher than those in the group without AVCD. Multiple regression analysis revealed that maximum HR and macro reentrant AT were significant predictors of AVCD. Receiver operating characteristic curve analysis revealed that Max HR of <165.0 bpm predicts AVCD with a sensitivity of 76.47% and a specificity of 74.00%. In patients with persistent AF, low Max HR and the presence of macro reentrant AT during the ablation procedure were predictors of AVCD.

The role of cardiopulmonary exercise testing in risk stratification and prognosis of atrial fibrillation: a scoping review of the literature

BACKGROUND

Cardiopulmonary exercise testing (CPET) is a significant tool for evaluating exercise capacity in healthy individuals and in various pulmonary and cardiovascular conditions, quantifying symptoms and predicting outcomes. Atrial fibrillation (AF) poses a significant burden on patients and health systems; a research marathon is ongoing for discovering the pathophysiologic substrate, natural history, prognostic tools and optimal treatment strategies for AF. Among the plethora of variables measured during CPET, there is a series of parameters of interest concerning AF.

METHODS

We conducted a scoping review aiming to identify significant CPET-related parameters linked to AF, as well as indicate the impact of other cardiac disease-related variables. We searched PubMed from its inception to 12 January 2022 for reports underlining the contribution of CPET in the assessment of patients with AF. Only clinical trials, observational studies and systematic reviews were included, while narrative reviews, expert opinions and other forms of manuscripts were excluded.

RESULTS

In our scoping review, we report a group of heterogeneous, thus noteworthy parameters relevant to the potential contribution of CPET in AF. CPET helps phenotype AF populations, evaluates exercise capacity after cardioversion or catheter ablation, and assesses heart rate response to exercise; peak VO₂ and VE/VCO₂, commonly measured indices during CPET, also serve as prognostic tools in patients with AF and heart failure.

CONCLUSIONS

CPET seems to hold a clinically important predictive value for future cardiovascular events both in patients with pre-existing cardiac conditions and in healthy individuals. CPET variables may play a fundamental role in the prediction of future AF-related events.

Prognostic Value of Heart Rate Reserve in Patients with Permanent Atrial Fibrillation during Dipyridamole Stress Echocardiography

In patients in sinus rhythm, a blunted heart rate reserve (HRR) during dipyridamole stress echocardiography (SE) is a prognostically unfavorable sign of cardiac autonomic dysfunction. In this study we sought to assess the prognostic meaning of HRR in patients with permanent atrial fibrillation (AF). The study population was made by 301 patients (176 men, age 73 ± 8 years) with suspected (n = 200) or known (n = 101) coronary artery disease and permanent AF who underwent high-dose dipyridamole SE. HRR was calculated on an average of 5 consecutive beats as the peak/rest ratio of HR from 12-lead EKG. During a median follow-up time of 77 months (first quartile 44, third quartile 115 months), 111 (37%) patients died. Receiver operating characteristics analysis identified HRR ≤1.17 as the best predictor of mortality. At multivariable analysis, HRR ≤1.17 (HR 1.75, 95% CI 1.17 to 2.62; p = 0.006) independently predicted mortality together with age (HR 1.09, 95% CI 1.06 to 1.13; p <0.0001), rest wall motion score index (HR 1.69, 95% CI 1.01 to 2.83; p = 0.04), and systemic hypertension (HR 1.76, 95% CI 1.06 to 3.00; p = 0.04). The annual mortality was 5.1% in the overall population, 7.0% in the 140 (46%) patients with abnormal HRR and 3.5% in the 161 (54%) patients with normal HRR. The 8-year mortality was 48% in patients with abnormal HRR and 18% in those with normal HRR (p <0.0001). In conclusion, patients with suspected or known coronary artery disease with permanent AF with a blunted HRR have an increased mortality. HRR outweighs inducible ischemia for prediction of survival. The assessment of HRR should become an integral part of dipyridamole SE reading also in AF.

Exercise chronotropic incompetence phenotypes the level of cardiovascular risk and exercise gas exchange impairment in the general population. An analysis of the Euro-EX prevention trial

BACKGROUND

Chronotropic insufficiency (CI) is defined as the inability of the heart to increase its rate commensurate with increased demand. Exercise CI is an established predictor of major adverse cardiovascular events in patients with cardiovascular diseases.

AIM

The aim of this study was to evaluate how exercise CI phenotypes different levels of cardiovascular risk and how it may better perform in defining cardiovascular risk when analysed in the context of cardiopulmonary exercise test (CPET)-derived measures and standard echocardiography in a healthy population with variable cardiovascular risk profile.

METHODS

Apparently healthy individuals (N = 702, 53.8% females) with at least one major cardiovascular risk factor (MCVRF; hypertension, diabetes, tabagism, dyslipidaemia, body mass index > 25), enrolled in the Euro-EX prevention trial, underwent CPET. CI was defined as the inability to reach 80% of the chronotropic index, that is, the ratio of peak heart rate - rest heart rate/peak heart rate - age predicted maximal heart rate (AMPHR: 220 - age), they were divided into four groups according to the heart rate reserve (<80%>) and respiratory gas exchange ratio (RER; < 1.05>) as a marker of achieved maximal performance. Subjects with a RER < 1.05 (n = 103) were excluded and the final population (n = 599) was divided into CI group (n = 472) and no-CI group (n = 177).

RESULTS

Compared with no-CI, CI subjects were more frequently females with a history of hypertension in a high rate. CI subjects also exhibited a significantly lower peak oxygen uptake (VO₂) and circulatory power and an echocardiographic pattern indicative of higher left atrial volume index and left ventricular mass index. An inverse stepwise relationship between heart rate reserve and number of MCVRFs was observed (one MCVRF: 0.71 ± 0.23; two MCVRFs: 0.68 ± 0.24, three MCVRFs: 0.64 ± 0.20; four MCVRFs: 0.64 ± 0.23; five MCVRFs: 0.57 ± 18; p < 0.01). In multivariate analysis the only variable found predicting CI was peak VO₂ (p < 0.05; odds ratio 0.91; confidence interval 0.85-0.97).

CONCLUSIONS

In a population of apparently healthy subjects, exercise CI is common and phenotypes the progressive level of cardiovascular risk by a tight relationship with MCVRFs. CI patients exhibit some peculiar abnormal exercise gas exchange patterns (lower peak VO₂ and exercise oscillatory ventilation) and echo-derived measures (higher left atrium size and left ventricle mass) that may well anticipate evolution toward heart failure.