Ventricular Arrythmia (VA) is a severely abnormal heart rhythm (arrhythmia) that, unless treated immediately, causes death. VF is responsible for 75% to 85% of sudden deaths in persons with heart problems.
To pump blood out to the body, all areas of the heart normally squeeze (contract) in a synchronised manner. The heart's upper chambers (the atria) contract first, and then the heart's bottom two chambers (the ventricles) contract. During VA, however, the ventricles contract independently of the atria, and some areas of the ventricles contract while others are relaxing, in a disorganized manner.
Ventricular arrhythmias are usually acute events with their incidence is related that of its causative pathology.
Most ventricular arrhythmias are caused by coronary heart disease, hypertension or cardiomyopathy.
Ventricular tachycardia
The heart rate is rapid, frequently 120 bpm and above. At this rate the ventricles do not have time to fill properly and cardiac output is reduced leading to hypotension. Fast VT is a peri-arrest rhythm and cardiac arrest may occur at anytime. Due to reduced cardiac output complications such as myocardial infarction can occur.
Cardiac failure can be precipitated by VT. VT sometimes reverts spontaneously or can be corrected with medical therapy.
Ventricular fibrillation
The heart rate is very rapid and irregular and no mechanical contraction fo the heart can occur. The patient is pulseless and rapidly loses consciousness and stops breathing. These rhythms do not revert spontaneously. This condition causes cardiac arrest.
Chest x-ray: may show evidence of congestive heart failure. Also, evidence of the underlying cardiac pathology may be seen such as ventricular enlargement.
Blood tests should exclude electrolyte imbalances.
Cardiac enzymes should be tested to establish whether an acute heart attack has occurred.
The prognosis of these arrhythmias is generally poor. Ultimately the prognosis depends on the nature of the underlying cause. The outlook for VT is slightly better than VF and some ventricular tachyarrhythmias (fast abnormal heart rates) are surprisingly well tolerated.
Cardioversion either with drugs (class one agents such as lignocaine) or DC shock. The patient should be resuscitated. Once the arrhythmia has been cardioverted, prophylaxis should be instigated to prevent recurrence (using agents such as beta-blockers). Patients whould also be placed on continuous cardiac monitoring and arrangements made for assessment by a cardiologist.
Hurst's The Heart 8th Edition, McGRAW-HILL 1994. Kumar and Clark Clinical Medicine 4th Edition, W.B SAUNDERS 1998. MEDLINE Plus.
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