Atrioventricular block

Cardiovascular

Clinicals - History

Fact Explanation
Symptoms of first degree heart block First degree heart block is usually asymptomatic. Patients may develop dyspnea, chest pain and syncope with exertion. Symptoms of first degree heart block
First degree heart block is usually asymptomatic. Patients may develop dyspnea, chest pain and syncope with exertion.
Symptoms of second degree heart block Second degree heart block can also be asymptomatic sometimes. Recurrent syncope or presyncope is another presentation of second degree heart block. Symptoms of second degree heart block
Second degree heart block can also be asymptomatic sometimes. Recurrent syncope or presyncope is another presentation of second degree heart block.
Symptoms of third degree heart block Patients with third degree heart block can present with recurrent syncope or presyncope. In complete heart block light headedness and dizziness are also usual complains. These symptoms are due to reduced cerebral perfusion secondary to bradycardia. Fatigue is commonly seen in patients with complete heart block. Symptoms of third degree heart block
Patients with third degree heart block can present with recurrent syncope or presyncope. In complete heart block light headedness and dizziness are also usual complains. These symptoms are due to reduced cerebral perfusion secondary to bradycardia. Fatigue is commonly seen in patients with complete heart block.
History of myocarditis or myocardial infarction Patients who had a history of myocarditis or myocardial infarction can later present with first degree atrio-ventricular block. History of myocarditis or myocardial infarction
Patients who had a history of myocarditis or myocardial infarction can later present with first degree atrio-ventricular block.
Irregular heart beat Patients with atrio-ventricular block may complain of irregular heartbeat. Irregular heart beat
Patients with atrio-ventricular block may complain of irregular heartbeat.
Drug history Certain drugs (digitalis, beta-blockers, and calcium channel blockers) can cause slow transmission through the atrioventricular node. Drug history
Certain drugs (digitalis, beta-blockers, and calcium channel blockers) can cause slow transmission through the atrioventricular node.
Angina Patients with a history of ischemic heart diseases may complain of frequent ischemic chest pain because bradycardia can precipitate angina. Angina
Patients with a history of ischemic heart diseases may complain of frequent ischemic chest pain because bradycardia can precipitate angina.
Sudden death Sudden death can occur due to asystole or secondary to ventricular tachyarrhythmias. Sudden death
Sudden death can occur due to asystole or secondary to ventricular tachyarrhythmias.

Clinicals - Examination

Fact Explanation
Signs of first degree heart block Cardiovascular examination can be normal in first degree atrioventricular block. Signs of first degree heart block
Cardiovascular examination can be normal in first degree atrioventricular block.
Signs of second degree heart block Bradycardia and irregular pulse can be detected. Signs of second degree heart block
Bradycardia and irregular pulse can be detected.
Signs of third degree heart block In third degree heart block, the right atrium can contract against the closed tricuspid valve. This results in appearance of cannon a waves in jugular venous pulsations. Signs of third degree heart block
In third degree heart block, the right atrium can contract against the closed tricuspid valve. This results in appearance of cannon a waves in jugular venous pulsations.

Investigations - Diagnosis

Fact Explanation
ECG In first degree heart block every P wave is followed by a QRS complex but the P-R interval is 0.21 sec or more. Mobitz type 1 and 2 are two types of second degree heart block. In Wenckebach phenomenon (Mobitz type I) PR interval progressively increases and there is a P wave which is not followed by a QRS complex. These ECG changes repeat cyclically. In Mobitz type two second degree heart block constant P-R interval is followed by a non-conducted QRS complex. In complete heart block there are more P waves than the QRS complexes, and there is no relationship between the P and QRS complexes. The ventricular beat may arise within the atrio-ventricular node resulting in narrow complex QRS waves and below the atrio-ventricular node resulting in wide QRS complexes. ECG
In first degree heart block every P wave is followed by a QRS complex but the P-R interval is 0.21 sec or more. Mobitz type 1 and 2 are two types of second degree heart block. In Wenckebach phenomenon (Mobitz type I) PR interval progressively increases and there is a P wave which is not followed by a QRS complex. These ECG changes repeat cyclically. In Mobitz type two second degree heart block constant P-R interval is followed by a non-conducted QRS complex. In complete heart block there are more P waves than the QRS complexes, and there is no relationship between the P and QRS complexes. The ventricular beat may arise within the atrio-ventricular node resulting in narrow complex QRS waves and below the atrio-ventricular node resulting in wide QRS complexes.
Holter monitoring If the ECG shows no abnormality it is better to proceed with a 24 hour Holter monitoring in order to identify transient atrio-ventricular blocks. Holter monitoring
If the ECG shows no abnormality it is better to proceed with a 24 hour Holter monitoring in order to identify transient atrio-ventricular blocks.
Electrophysiologic testing This is an invasive procedure and can detect conduction abnormalities in His bundles. Electrophysiologic testing
This is an invasive procedure and can detect conduction abnormalities in His bundles.
Exercise ECG Exercise ECG helps in detecting exercise induced arrhythmias. Exercise ECG
Exercise ECG helps in detecting exercise induced arrhythmias.
Serum electrolytes Electrolyte abnormalities can also cause reversible atrioventricular blocks. Serum electrolytes
Electrolyte abnormalities can also cause reversible atrioventricular blocks.
Thyroid function test Thyroid function abnormalities can cause atrio-ventricular block. Thyroid function test
Thyroid function abnormalities can cause atrio-ventricular block.

Investigations - Management

Fact Explanation
ECG Patients with first degree heart block need long term monitoring because of the reason it may progress to second degree heart block. ECG
Patients with first degree heart block need long term monitoring because of the reason it may progress to second degree heart block.
Holter monitoring This is also recommended for patients with first degree heart block for the above mentioned reason. Holter monitoring
This is also recommended for patients with first degree heart block for the above mentioned reason.

Management - Supportive

Fact Explanation
Health education First degree heart block usually does not require any treatment. Once a pacemaker is inserted patient should avoid weight lifting from the ipsilateral arm for about 4 to 6 weeks. Patients should be followed up in every 3 to 6 months. Health education
First degree heart block usually does not require any treatment. Once a pacemaker is inserted patient should avoid weight lifting from the ipsilateral arm for about 4 to 6 weeks. Patients should be followed up in every 3 to 6 months.
Stop or change any offending drugs Digitalis and calcium channel blockers can cause atrio-ventricular block. If recognised the drug should be stopped. Stop or change any offending drugs
Digitalis and calcium channel blockers can cause atrio-ventricular block. If recognised the drug should be stopped.
Correct any electrolyte imbalance Electrolyte imbalance is a potentially reversible cause of atrio-ventricular block. Correct any electrolyte imbalance
Electrolyte imbalance is a potentially reversible cause of atrio-ventricular block.

Management - Specific

Fact Explanation
Conservative management Patients with first degree atrio-ventricular block are usually asymptomatic and does not require any treatment. Conservative management
Patients with first degree atrio-ventricular block are usually asymptomatic and does not require any treatment.
Permanent pacing Temporary transcutaneous or transvenous pacing may be needed in emergency situations. For first degree heart block permanent pacing is considered if they have congestive heart failure or left ventricular dysfunction, because bradycardia can further compromise the cardiac function. Pacing is also considered in patients with bi-fascicular or tri-fascicular block with first degree heart block. The definitive treatment for symptomatic (heart failure or ventricular arrhythmias, symptomatic bradycardia) atrio-ventricular blocks, particularly for third degree atrio-ventricular blocks is the implantation of a permanent pacemaker. In patients with second or third degree heart block permanent pacing is indicated if the asystole is greater than or equal to 3.0 seconds or if escape rate is less than 40 bpm, even the patient is asymptomatic. If the patient has symptomatic heart failure with atrio-ventricular block, biventricular pacing is considered to be superior to conventional right ventricular pacing. Permanent pacing
Temporary transcutaneous or transvenous pacing may be needed in emergency situations. For first degree heart block permanent pacing is considered if they have congestive heart failure or left ventricular dysfunction, because bradycardia can further compromise the cardiac function. Pacing is also considered in patients with bi-fascicular or tri-fascicular block with first degree heart block. The definitive treatment for symptomatic (heart failure or ventricular arrhythmias, symptomatic bradycardia) atrio-ventricular blocks, particularly for third degree atrio-ventricular blocks is the implantation of a permanent pacemaker. In patients with second or third degree heart block permanent pacing is indicated if the asystole is greater than or equal to 3.0 seconds or if escape rate is less than 40 bpm, even the patient is asymptomatic. If the patient has symptomatic heart failure with atrio-ventricular block, biventricular pacing is considered to be superior to conventional right ventricular pacing.
Medical management Medical management has very limited role in treating atrio-ventricular block. It can be used in first degree heart block. Atropine and isoproterenol are commonly used drugs. Medical management
Medical management has very limited role in treating atrio-ventricular block. It can be used in first degree heart block. Atropine and isoproterenol are commonly used drugs.

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