Prevention of Heart Block.
Prevention as pertains to heart block means prevention of either uncomfortable symptoms or dangers that run from dizziness to sudden cardiac death.
The range of heart block disease begins with first degree heart block, in which there are usually no symptoms, to second degree, in which patients may complain of palpitations and shortness of breath, to late second degree and third degree, in which there there may be life-threatening arrhythmias that interfere with cardiac output.
First Degree Heart Block
- Asymptomatic first degree heart block: Requires no treatment beyond mere follow-up and continued surveillance for the emergence of inconvenient or concerning symptoms.
- Symptomatic first degree heart block: Can present as “pacemaker syndrome” which is the frightening awareness of one’s own heart beat. Based on patient preference after informed consent, risks vs benefits of general anesthesia and implantable devices, and patient-perceived quality of life so affected, a permanent implantable pacemaker can be placed to counter the arrhythmia.
Second Degree Heart Block: Mobitz I
Like asymptomatic first degree heart block, asymptomatic Mobitz I patients require no treatment.
- Symptomatic Mobitz I patients: Can be treated with medicinal pacing of the ventricles, using atropine (anticholinergic) or dopamine (adrenergic agonist); or temporary cardiac pacemaking in cases of myocardial infarction to mitigate the mortality risk associated with a Mobitz 1 arrhythmia coincident with a myocardial infarction.
Symptomatic patients that have a reversible cause (medication, electrolyte imbalance, or athleticism) are treated by reversing this cause. Also symptomatic patients with a non-reversible cause can have a permanent pacemaker implanted.
Second Degree Heart Block: Mobitz II
- If a patient has Mobitz II arrhythmia due to reversible hyperkalemia, the potassium should be addressed, which often coincides with insulin management of hyperglycemia in diabetics
- Stable patients: Stable Mobitz II patients do not require immediate pharmacologic or pacemaker therapy, but they should be observed closely because Mobitz II itself is unstable and can progress to complete (third degree) heart block
- Symptoms from even a stable bradycardia will require an implantable pacemaker.
- Unstable patients: in cases in which are present hypotension, altered mental status, shock, chest pain, or pulmonary edema, immediate pharmacologic therapy (atropine) and a temporary pacemaker are required to increase heart rate and cardiac output. Once stable, any potentially reversible causes should be treated, followed by a permanent pacemaker, especially in patients without a reversible cause of the arrhythmia
- Patients with a high grade AV block (advanced Mobitz II, with more than one dropped beat) require permanent implantable pacemakers
Third Degree Heart Block: Complete Heart Block
In many ways, management of third degree AV (complete) block is the same as for second degree Mobitz II AV block:
- Stable Patients: Since ventricular escape rhythms are unreliable and unstable, patients should be monitored continuously in the event of deterioration. Any symptoms due to bradycardia should indicate a need for a permanent implantable pacemaker for the prevention of adverse cardiac events
- Unstable Patients: Hemodynamic instability mandates urgent, emergency treatment with atropine and a temporary cardiac pacemaker (transcutaneous or transvenous). Dopamine can be given for those with hypotension. Once stability is achieved, a permanent pacemaker can be placed