Degrees of blockade
The first degree only means an increase in conduction time: all impulses reach the ventricles, the pulse is normal, and there are usually no complaints. The second degree is divided into two types: with the first, the delay increases from beat to beat until one contraction falls out - this option is often benign; in the second type, contractions occur suddenly, without warning, and the risk of progression is high. In the third, complete block, the atria and ventricles work independently of each other, and the ventricular rate drops to dangerously low levels.
- 1st degree: prolongation of the PQ interval, no complaints
- 2nd degree, Mobitz type I: gradual lengthening with loss of contraction
- 2nd degree, type Mobitz II: sudden loss, dangerous option
- 3rd degree: complete blockade, independent ventricular rhythm
- The blockage may be permanent or transient
Reasons
In the elderly, age-related sclerotic changes in the conduction system are most often to blame. In young people, blockade of the first degree and Mobitz type I is often associated with high tone of the vagus nerve and occurs in athletes at night, without being a disease. Acutely developed blockade occurs during myocardial infarction, myocarditis, after heart surgery and catheter interventions. The medicinal cause is very important: beta blockers, some antiarrhythmic drugs and digitalis preparations can cause a blockade, which disappears after correction of treatment.
- Age-related fibrosis of the conduction system
- Myocardial infarction, especially the inferior wall
- Myocarditis, including after infections
- Surgeries and catheter interventions on the heart
- Beta blockers, digoxin, some antiarrhythmics
- High vagal tone in athletes
- Increased blood potassium, hypothyroidism
Symptoms
In the first degree and often in Mobitz type I, the person does not feel anything, and the blockade is found by chance on an ECG before surgery or during a physical examination. Symptoms appear when the pulse becomes rare: weakness increases, exercise tolerance decreases, dizziness and darkening occur. The most dangerous manifestation of complete blockade is sudden fainting with pallor, sometimes with convulsions, after which consciousness quickly returns. Such an episode requires immediate hospitalization.
- Most often asymptomatic in grade 1
- Weakness, fatigue, shortness of breath on exertion
- Dizziness, darkening of the eyes
- Feeling of freezing and interruptions
- Sudden fainting in severe forms
- Confusion in the elderly
Diagnostics
The main method is an ECG, where characteristic changes in intervals and loss of complexes are visible. Since the blockade is transient and often worsens at night, daily ECG monitoring with a diary of well-being is required. An echocardiogram shows the condition of the heart muscle and valves and helps find the cause. Additionally, blood potassium, thyroid function, signs of a previous heart attack and inflammation are assessed. Be sure to review the entire list of medications taken.
- 12-lead ECG
- Daily ECG monitoring
- EchoCG
- Exercise test according to indications
- Blood potassium, thyroid hormones
- Markers of myocardial damage in acute onset
- Review of medications taken
Treatment and observation
A first-degree block without symptoms does not require treatment - observation and periodic ECG are needed. In Mobitz type I, tactics depend on complaints and pulse rate. Mobitz type II and complete block are considered an indication for implantation of a permanent pacemaker because the risk of sudden pauses is high and medications do not solve the problem. If the block is caused by a drug or a reversible cause, it is first removed and the rhythm reassessed. In acute infarction, temporary stimulation is sometimes used until the condition stabilizes.
- Observation and control ECG in grade 1
- Cancellation or replacement of the drug according to the doctor’s decision
- Correction of potassium and thyroid function
- Pacemaker implantation for Mobitz II and complete blockade
- Temporary stimulation in acute situations
- Treatment of underlying heart disease
- Do not take medications for blood pressure and pulse unless prescribed
