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............................................................................................................................................................................. 3.4.3 Cardiac resynchronization therapy (endo- and/or epicardial) Cardiac dyssynchrony is a difference in the timing of electrical and mechanical activation of the ventricles, which can result in impaired cardiac efficiency. CRT delivers biventricular pacing to correct electromechanical dyssynchrony in order to increase cardiac output.36 In multiple trials, CRT has shown a significant morbidity and mortality benefit in specific patient groups with reduced left ventricular ejection fraction (LVEF).3740

3.4.4 Alternative methods (conduction system pacing, leadless pacing) 3.4.4.1 Conduction system pacing Compared with right ventricular (RV) pacing, His bundle pacing (HBP) provides a more physiological simultaneous electrical activation of the ventricles via the HisPurkinje system. HBP can restore conduction in a subset of patients with high-degree AVB, and shorten QRS duration in some patients with left bundle branch block (LBBB) or right bundle branch block (RBBB).4144 More studies are ongoing and required to evaluate whether HBP has clinical benefits over CRT or RV pacing. In addition, left bundle branch area pacing is being studied as a pacing modality for patients in whom the conduction disease is too distal for HBP (see section 7.3).

3.4.4.2 Leadless pacing Miniaturized, intracardiac leadless pacemakers have been introduced. These devices are inserted percutaneously through the femoral vein and implanted directly in the RV wall using customized catheterbased delivery systems. The first-generation leadless pacemakers have been proven to provide effective single-chamber pacing therapy.4550 Albeit a promising technology, potential difficulty with leadless pacemaker retrieval at the end of service is a limitation. Thus far, there are no randomized controlled data available to compare clinical outcomes between leadless pacing and single-chamber transvenous pacing.

3.4.5 Pacing modes Technological advances in pacemaker therapy have resulted in a wide variety of pacing modalities. Pacemakers can sense the heart’s intrinsic electrical activity and restore the rate and AV sequence of cardiac activation. Abnormal cardiac automaticity and conduction may be treated by single-lead atrial sensing/pacing, single-lead ventricular sensing/pacing, single leads that pace the right ventricle (RV) and sense both the atrium and ventricle, and dual-lead systems that sense and pace the right atrium (RA) and RV. For common pacing modes, refer to Supplementary Table 2. The choice of the optimal pacing mode in the presence of conduction disturbances is driven by the underlying morbidity, the impact of pacing therapy on morbidity, and the potential harmful effect of the chosen pacing modality. The choice of pacing modes in specific situations is discussed in section 5.

3.4.6 Rate-responsive pacing The sinus node modulates the heart rate during different types and loads of exercise (i.e. physical exercise, emotions, postural change, and fever) proportional to the metabolic demand. Rate-responsive pacemaker systems strive to produce an appropriate compensatory heart rate during emotional or physical activity by sensing body motion/acceleration, minute ventilation, intracardiac impedance, or other surrogates of physical and mental stress, and are indicated in cases of chronotropic incompetence.5157 Dual-sensing rate-responsive pacing (e.g. accelerometer and minute ventilation) may be used in selected patients.58 A brief overview of the most commonly used rate-responsive pacing sensors is given in Supplementary Table 3.

3.5 Sex differences

Pacing indications and complication rates differ between male and female patients. In male patients, primary pacemaker implantation is more often indicated for AVB and less so for SND and atrial fibrillation (AF) with bradycardia.59,60 In female patients, the rate of procedure-related adverse events is significantly higher, corrected for age and type of device. This higher rate is driven mostly by pneumothorax, pericardial effusion, and pocket haematomas.5961 Possible explanations for this are a smaller body size in women and anatomical differences, such as smaller vein diameters and RV diameters.

4 Evaluation of the patient with

suspected or documented bradycardia or conduction system disease

4.1 History and physical examination

A careful history and physical examination are essential for the evaluation of patients with suspected or documented bradycardia (Figure 3). Current guidelines emphasize the importance of the history and physical examination in the initial evaluation, particularly for identifying patients with structural heart disease.62,63 A complete history should include family history, comprehensive cardiovascular risk assessment, and recent/historical diagnoses that may cause bradycardia. The history should be focused on frequency, severity, and duration of symptoms that might suggest bradycardia or conduction system disease. The relationship of symptoms to physical activity, emotional distress, positional changes, medical treatment (Table 6), and typical triggers (e.g. urination, defecation, cough, prolonged standing, and shaving) should be explored too, as well as pulse rate if measured during an episode. Family history may be especially important in young patients with progressive cardiac conduction disease either isolated or in association with cardiomyopathies and/or myopathies.64,65 Physical examination should focus on manifestations of bradycardia and signs of underlying structural heart disease or systemic disorders (Table 7). Symptomatic slow peripheral pulses should be confirmed with cardiac auscultation or ECG to ensure that other rhythms are not misrepresented as bradycardia (e.g. premature ventricular contractions). Autonomic regulation disorders are important in the differential diagnosis of syncope or near syncope, and, therefore, orthostatic changes in heart rate and blood pressure may help in the evaluation of the patients. Downloaded from academic.oup.com/eurheartj/article/42/35/3427/6358547 by guest on 07 October 2026