Age‐Related Variations in Ventricular Response Rate in Individuals with Persistent or Permanent Atrial Fibrillation

Abstract

To the Editor: Atrial fibrillation (AF) is the most frequent sustained arrhythmia.1 Its prevalence increases with age, affecting almost 20% of individuals aged 85 and older2 and resulting in substantial health care use and morbidity.3 Rapid heart rate (HR) is the most obvious cause of symptoms, which in turn are associated with lower quality of life and higher risk of hospitalization.4 The influence of age on ventricular rate has been previously investigated in individuals with paroxysmal AF5 but has not been well characterized in those with persistent or permanent AF. Thus, the goal was to evaluate the effect of age on ventricular response rate in these individuals. Thirty-two thousand seven hundred seventeen 24-hour electrocardiographic Holter recordings were performed in the Complexo Hospitalario Universitario A Coruña, Instituto de Investigación Biomédica de A Coruña, A Coruña, Spain, between March 1, 2000, and November 14, 2015. Those in which AF was verified were initially considered for inclusion in this study. When several Holter monitoring studies were available for the same individual, the first was selected, resulting in 3,109 available recordings with AF. Individuals in whom AF was not the sole cardiac rhythm identified throughout the recordings or in whom a pacemaker had been previously implanted were also excluded (n = 701), leaving a final study population of 2,408 individuals. Maximal, minimal, and mean HR over the 24-hour period were collected for each Holter recording. HR range was estimated as the difference between maximal and minimal HR. Correlations between age and HR were assessed using Spearman rank correlation coefficients. Age was categorized into four groups (<50, 50–64, 65–79, ≥80), and trends in HR were assessed according to age group. The relationship between age and the need for pacemaker implantation within 1 year was also evaluated in the subset of 2,178 participants with AF who underwent Holter monitoring between March 1, 2000, and November 14, 2014. The statistical significance of trends across age intervals was assessed using the Cochran-Armitage test for categorical variables and the Cuzick nonparametric test for continuous variables. The ethics committee of A Coruña-Ferrol approved this study. Mean age was 75 ± 10, and 1,381 subjects (57.4%) were male. Maximal HR was 134 ± 32 beats per minute (bpm), minimal HR was 41 ± 11 bpm, and mean HR was 74 ± 17 bpm. There were significant inverse correlations between age and maximal HR (ρ = −0.306, P < .001), minimal HR (ρ = −0.149, P < .001), mean HR (ρ = −0.230, P < .001), and HR range (ρ = −0.303, P < .001). Table 1 shows the trends in maximal, minimal, and mean HR and HR range according to age group; all these parameters decreased gradually and significantly with age. The likelihood of pacemaker implantation within 1 year after Holter recordings also increased progressively with age, (<50, 4.7%; 50–64, 5.4%; 65–79, 8.7%; ≥80, 10.2%; P for trend <.001). An inverse association was found between age and ventricular rate in individuals with persistent or permanent AF. The need for pacemaker implantation in these individuals also increased progressively with age. Although age has been shown to influence HR during episodes of paroxysmal AF,5 this study complements and expands this observation to individuals with persistent or permanent AF. The slower ventricular rate with increasing age in these subjects may mainly be due to progressive atrioventricular conduction delay6 and atrial structural changes. Impaired atrioventricular conduction or age-related decreases in sinus node function may also explain the gradual increase in the probability of pacemaker implantation during follow-up in individuals with AF.7 A lower level of physical activity in older adults might further account for the greater reduction in maximal and mean HR with age than in minimal HR. The decrease in minimal HR with increasing age occurred despite well-known higher vagal tone at rest in younger individuals. One might infer that the dosage of negative chronotropic drugs required for adequate HR control in elderly adults might be lower and that these medications may be associated with greater probability of symptomatic bradycardia than in their younger counterparts. Nonetheless, no attempt was made to account for the effect of such medications, and the study was not designed to test these assertions. Furthermore, the indications for pacemaker implantation were not evaluated. In conclusion, HR tended to decrease with age in individuals with persistent or permanent AF, and there was an apparently congruent, gradual increase in the need for pacemaker implantation with aging in these individuals. Conflict of Interest: The authors declare no competing interests. Author Contributions: Bouzas-Mosquera: study concept and design, acquisition of subjects and data, analysis and interpretation of data, preparation of manuscript. Broullón, Martínez, Yáñez, Álvarez-García, Peteiro, Vázquez-Rodríguez: acquisition of subjects and data, review of manuscript. Sponsor's Role: The study had no external funding.