Author + information
- L. Marques,
- A. Castro,
- R. Santos,
- H. Guedes,
- D. Seabra,
- R. Sousa and
- P. Pinto
Slow heart rate is a common cause for hospital referral and cardiologist evaluation in the emergency department. In many patients (pts), a potential reversible cause for bradycardia can easily be identified, and permanent pacing should be delayed until the correction of these underlying conditions. Medications and electrolyte disturbances are among the major reversible causes for conduction system disturbances. Still, many of these pts may have underlying conduction system disease, with a potential need to a permanent cardiac pacemaker (PM) implantation at a long-term. The identification of this subgroup of pts remains a challenge.
To characterize a cohort of pts admitted to a cardiology ward with a diagnosis of bradycardia in the context of negative chronotropic medication intake and/or electrolyte disturbances, and to identify prognostic features that may be associated with permanent PM implantation.
We retrospectively analysed a group of pts admitted to a cardiology department with an initial diagnosis of bradycardia in the context of medication intake and/or electrolyte disturbances, between 1/2012 and 9/2016. Clinical characteristics [age, sex], conduction disorder on first medical contact [sinus node disfunction (SND), atrioventricular block (AVB), atrial fibrillation/flutter with low ventricular rate (AF/AFL with LVR)], outpatient medication [beta blockers, digoxin, beta blockers with digoxin, amiodarone, others], electrolytic disturbances [hyperkalemia] and evidence of structural heart disease [coronary disease; native heart valve disease; heart valve prothesis; dilated cardiomyopathy; hypertensive heart disease] were analysed. The primary end point was permanent PM implantation, in hospitalization or after discharge. Percentage of atrial and ventricular pacing was analysed at 1, 8 and 24 weeks of follow-up.
A total of 121 pts were included (41.3% male; mean age 79.9±8.3 years). On first medical contact, SND was diagnosed in 8 (6.6%), AF/AFL with LVR in 34 (28.1%) and AVB in 79 (65.4%) pts. Regarding the reversible causes of bradycardia, drug intake was identified in 113 (93.4%) and hyperkalemia in 8 (6.6%); among medications, beta blockers were the most common (77; 68.1%), followed by digoxin (15; 13.3%), beta blockers in association with digoxin (10; 8.8%), amiodarone (4; 3.5%) and other agents (7; 6.2%; including ivabradine, flecainide, propafenone, diltiazem, verapamil). Drug discontinuation or potassium correction reversed the conduction disturbance in 16 (13.2%) pts; permanent PM was needed in 105 (86.8%), with implantation occurring during hospital admission in 98 (93.3%) and after discharge in 7 (6.7%), after a mean follow-up of 9.7 months. Patients without need of permanent PM were more frequently woman (87.5% vs. 12.5%, p=0.012) and had higher prevalence of AF/AFL (81.3% vs 18.8%, p=0.005), with no significant differences on age (p=0.085), conduction disturbance on first medical contact (p=0.081), evidence of structural heart disease (p=0.874), outpatient medication or electrolyte disturbances (p=0.068), need for temporary transvenous PM (p=0.775), nor beta blockers dosage on admission (p=0.893 for bisoprolol; p=0.217 for carvedilol); although, a lower dosage of digoxin intake on admission predicted the need for permanent PM placement (0.21±0.06 vs. 0.16±0.06mg, p=0.029).
AVB was the most frequent conduction disturbance identified in this cohort and beta-blockers were the most common reversible cause for bradycardia. Even with the identification and correction of a reversible cause, many pts kept indication for permanent PM, which globally defines these pts as a group of risk who deserve further follow-up for conduction disturbances. The presence of AF/AFL predicted a lower need for permanent PM, as well as the intake of higher dosages of oral digoxin as precipitating factor. Further studies, with larger cohorts and longer follow-up are needed, in order to define better predictors for early PM implantation.