Bradycardia

Physiological Bradycardias

Some bradycardias are considered normal and do not require treatment:

• Athlete’s bradycardia: Intensive and regular physical training leads to an adaptation of the heart with increased vagal tone and a higher stroke volume, allowing the heart to pump more efficiently at lower rates;
• Nocturnal bradycardia: During sleep, the slowing of metabolic activity and the predominance of the parasympathetic nervous system cause a physiological decrease in heart rate;
• Vagal reactions: Certain situations, such as intense pain, strong emotion, or straining during defecation, can trigger a vagal reflex with transient bradycardia.

Pathological Bradycardias

Pathological bradycardias can result from different mechanisms:

• Sinus node dysfunction: Also called sick sinus syndrome, it corresponds to impaired function of the sinus node. It may manifest as inappropriate sinus bradycardia, sinus pauses, or brady-tachy syndrome (alternating slow and fast phases);
• Atrioventricular (AV) blocks: Characterized by a slowing or interruption of conduction between the atria and ventricles. There are three degrees:
  • First-degree AV block: Simple slowing of conduction (prolonged PR interval > 200 ms);
  • Second-degree AV block: Intermittent blockage of some atrial impulses, with two main types (Mobitz I or Wenckebach phenomenon, and Mobitz II);
  • Third-degree AV block or complete heart block: No atrial impulse reaches the ventricles, which beat at their own slow intrinsic rate (30–40 beats/minute).

Secondary Causes

Many factors can cause or worsen bradycardia:

• Medications: Beta-blockers, bradycardia-inducing calcium channel blockers (diltiazem, verapamil), digoxin, amiodarone, ivabradine, certain psychotropic drugs;
• Metabolic disorders: Hypothyroidism, hyperkalemia, hypermagnesemia, hypothermia;
• Cardiac diseases: Ischemic heart disease (myocardial infarction, particularly inferior), cardiomyopathies, myocarditis, endocarditis, infiltrative diseases (amyloidosis, sarcoidosis);
• Neurological causes: Intracranial hypertension, increased vagal tone, sleep apnea;
• Degenerative causes: Aging of the conduction system (Lenègre’s or Lev’s disease), the main cause of AV block in elderly patients.

This last cause is particularly common in older patients seen at the Centre Cœur et Santé Bernouilli (Paris 8th), where regular follow-up helps monitor the progression of these conduction disorders.

The clinical presentation of bradycardias is highly variable, ranging from the complete absence of symptoms to severe manifestations that can be life-threatening:

• Asymptomatic forms: common in moderate or physiological bradycardias, discovered incidentally during a routine examination;
• Fatigue and exercise intolerance: reduced physical performance, fatigue, shortness of breath on exertion due to the heart’s inability to sufficiently increase its output (chronotropic incompetence);
• Neurological manifestations: dizziness, lightheadedness, concentration difficulties, psychomotor slowing;
• Presyncope and syncope: brief loss of consciousness linked to transient cerebral hypoperfusion. Stokes-Adams syncope, typical of complete AV blocks, is particularly abrupt and without warning;
• Heart failure: chronic bradycardia can contribute to heart failure through a prolonged reduction in cardiac output;
• Chest pain: a heart rate that is too low can trigger or worsen angina in patients with coronary artery disease (bradycardia-induced angina).

The severity of symptoms depends on several factors: the depth of the bradycardia, its duration, the presence of prolonged pauses, as well as the patient’s comorbidities. For example, a moderately slow heart rate that is well tolerated in a young person may cause significant symptoms in an older individual or someone with heart disease.

Emergency situations

Some presentations of bradycardia are true emergencies:

• Bradycardia with hemodynamic instability (hypotension, signs of shock);
• High-degree AV blocks with a very slow or unstable escape rhythm;
• Bradycardia with prolonged pauses (> 3 seconds);
• Brady-tachy syndrome with significant post-tachycardia pauses.

These situations, requiring urgent management, can be treated at Institut Mutualiste Montsouris (Paris 14th), which has a specialized interventional electrophysiology unit.

Main diagnostic methods

Diagnosis is based on several complementary tests, adapted to the clinical context:

• The standard electrocardiogram (ECG) is the first-line examination. It confirms bradycardia and identifies its mechanism (sinus bradycardia, AV block, etc.). The ECG also helps detect associated signs that may point to specific causes (post-myocardial infarction changes, ventricular hypertrophy, etc.);
• The Holter ECG: continuous recording of the heart’s electrical activity for 24 to 48 hours. This test is particularly useful for detecting paroxysmal episodes of bradycardia or for documenting nocturnal pauses. It also allows assessment of the average heart rate over 24 hours and its variability during daily activities.

These two tests are available in all Rythmopôle Paris centers, including at Cardiopôle Yvart (Paris 15th) and Centre Damrémont (Paris 18th).

Additional tests

For more complex cases, or when the diagnosis remains uncertain, more specialized examinations may be indicated:

• Implantable Holter: this small device, implanted under the skin, provides continuous electrocardiographic recording over several months. It is particularly useful for documenting bradycardias or syncopes that are widely spaced over time;
• Intracardiac electrophysiological study: performed via the femoral vein under local anesthesia, this invasive procedure allows precise assessment of sinus node function and atrioventricular conduction. It is indicated in cases of unexplained syncope with suspected conduction disorder, or to determine the exact level of an AV block;
• Exercise stress test: assesses the heart rate response to exercise (chronotropic response) and may reveal conduction disorders that appear or worsen during exertion;
• Tilt test: useful for diagnosing reflex syncopes with a cardioinhibitory component (bradycardia or vagally induced asystole).

These specialized tests are performed at Institut Mutualiste Montsouris by the electrophysiologists of Rythmopôle Paris.

In addition to rhythm evaluation, blood tests (thyroid function, electrolyte panel, kidney function) and echocardiography are generally performed to identify an underlying cause and assess overall cardiac function.

Risk stratification is an essential step in determining the need for and urgency of treatment. It is based on several criteria:

• Severity of bradycardia: very low heart rates (< 40 bpm) and prolonged pauses (> 3 seconds) are associated with a higher risk of complications;
• Presence and intensity of symptoms: symptomatic bradycardia (syncope, heart failure) represents a higher level of risk than asymptomatic bradycardia;
• Mechanism: certain conditions, such as high-degree AV block or Mobitz II AV block, carry a risk of progression to complete block and asystole;
• Site of the block: infra-Hisian blocks (in the His bundle or its branches) have a less favorable prognosis than nodal blocks;
• Clinical context: age, comorbidities, medication, high-risk professional activities (driving, working at heights, etc.);
• Underlying etiology: some causes, such as electrolyte disturbances or medication effects, are reversible, while degenerative or infiltrative diseases tend to progress.

This risk assessment helps guide therapeutic decisions, particularly the indication for pacemaker implantation. The electrophysiologists at Rythmopôle Paris specialize in this personalized risk evaluation.

Main treatments

The management of bradycardias is based on three main strategies:

• Treating the underlying cause: when a reversible cause is identified, correcting it is the priority:
  • Adjustment or discontinuation of bradycardia-inducing medications;
  • Correction of metabolic disorders (hyperkalemia, etc.);
  • Treatment of hypothyroidism;
  • Management of sleep apnea;
  • Treatment of infectious or inflammatory heart diseases.
• Temporary cardiac pacing: in cases of severe, poorly tolerated bradycardia while awaiting resolution of a reversible cause or implantation of a permanent pacemaker:
  • Drug therapy (atropine, isoprenaline);
  • External transcutaneous pacing;
  • Temporary endocardial pacing lead.
• Permanent cardiac pacing: the implantation of a pacemaker is the standard treatment for symptomatic bradycardias without a reversible cause. It is particularly indicated in:
  • High-degree or complete atrioventricular block;
  • Symptomatic sinus node dysfunction;
  • Persistent bradycardias with hypoperfusion symptoms;
  • Certain cases of recurrent, severe reflex cardioinhibitory syncope.

Pacemaker implantation is performed at Institut Mutualiste Montsouris by the electrophysiologists of Rythmopôle Paris. This procedure is carried out under local anesthesia with light sedation and generally requires only a short hospital stay. It is important to note that this treatment concerns only a small number of patients with significant, symptomatic

Physical activity

The impact of bradycardia on physical activity depends on its cause and severity:

• Physiological bradycardias in athletes do not require any restrictions and are even associated with better cardiovascular performance;
• For pathological bradycardias treated with a pacemaker, regular and moderate physical activity is encouraged after the post-implantation healing period (about 1 month);
• Certain sports with a risk of direct impact on the pacemaker device (combat sports, rugby, etc.) may be discouraged;
• A cardiac rehabilitation program may be offered at Cardiopôle Yvart for patients after pacemaker implantation, to gradually resume appropriate physical activity.

Professional life

In most cases, well-managed bradycardia does not cause significant professional limitations:

• After pacemaker implantation, a short work leave (2 to 4 weeks) is generally recommended;
• Certain professions involving particular risks (professional driving, piloting, working at heights) may be subject to temporary or permanent restrictions, depending on the type of bradycardia and the treatment implemented;
• Specific recommendations regarding exposure to certain electromagnetic environments may be made for pacemaker wearers.

Daily life

For patients with a pacemaker:

• Driving is generally allowed one week after implantation for light vehicles, with longer restrictions for heavy vehicles;
• Certain precautions regarding electromagnetic fields are recommended: avoid carrying mobile phones directly over the pacemaker, maintain a safe distance from certain industrial electrical devices;
• MRI scans are possible with most modern (MRI-compatible) pacemakers, under specific conditions and with special programming;
• Passing through security gates (airports, stores) is allowed but may trigger alarms; a pacemaker identification card is provided to the patient.

With appropriate and personalized management, the vast majority of patients with bradycardia can lead an active life without major restrictions.

Rythmopôle Paris offers comprehensive expertise in the management of bradycardia:

• A team of experienced electrophysiologists specializing in the diagnosis and treatment of cardiac rhythm disorders;
• Fully equipped technical facilities for carrying out all examinations required for the precise diagnosis of bradycardia;
• Expertise in pacemaker implantation at Institut Mutualiste Montsouris;
• Personalized patient follow-up, including implantable device checks, in several centers across the Île-de-France region, including Centre Cœur et Santé Bernouilli and Cardiopôle Peupliers-Trubert;
• A multidisciplinary approach allowing for the management of associated cardiac conditions;
• Access to advanced technologies such as remote monitoring of pacemakers.