Ventricular Fibrillation, Clinical Manifestation, Diagnosis, And Treatment Of Atrial Fibrillation
Manifestation And Management
This is the commonest fatal arrhythmia in ischemic heart disease. The myocardium of the ventricles contract asynchronously and fractionally to produce a fibrillary movement without any sustained synchronous beat. Pumping action of the heart stops and the circulation comes to a standstill and death ensures if resuscitatory measures are not instituted immediately.
The physical signs are exactly those of cardiac asystole. The ECG distinguishes ventricular fibrillation from standstill.
Management: Electrocardiogram is mandatory for diagnosis. Ventricular fibrillation is recognized on the ECG by the absence of QRS complexes and T-waves and the presence of low amplitude baseline undulations which are quite variable both in amplitude and rhythm. The heart is defibrillated by direct currect (DC) shock of 300-400 Joules. Management of VF is the same as that for suddent cardiac arrest.
Bretylium tosylate given intravenously in dose of 5-10 mg/kg body weight is very effective in preventing the recurrence of ventricular fibrillation.
Atrial Fibrillation Leading To Stroke
The onset of atrial fibrillation may be felt as palpitation, especially so if the heart rate is high. The pulse is totally irregular in rhythm and volume (irregularly irregular). Pulse deficit can be made out by simultaneous palpation of the pulse and auscultation of the heart rate (by two different observers). A difference of more than 10 beats per minute is highly suggestive of atrial fibrillation. The irregularity increases with exertion. Auscultation reveals total irregularity and varying intensity of the first heart sound. The ‘a’-wave of the jugular venous pulse is abolished. The presystolic accentuation of the mid-diastolic murmur of mitral stenosis disappears. Confirmation of the diagnosis is made by ECG which shows absence of P-waves and the presence of fibrillary waves instead. The QRS complexes are irregular in rhythm and amplitude but normal in pattern.
Differential diagnosis: Frequently occurring irregular extrasystole may be mistaken for AF, especially if the heart rate is slow. Exercise abolishes the extrasystoles whereas it aggravates atrial fibrillation. In a few cases where clinical distinction Is difficult, electrocardiogram is needed for final diagnosis.
Course and prognosis: When the underlying condition is reversible such as myocarditis, pneumonia or thyrotoxicosis, treatment of the primary cause corrects the AF also. In chronic conditions, such as valvular or congenital heart disease, cardiomyopathy and ischemic heart disease, the arrhythmia tends to persist even after treatment of the primary disease. Atrial fibrillation gives rise to thrombo-embolic episodes, especially so when there is obstruction to atrioventricular flow as in mitral stenosis. Occurrence of atrial fibrillation leads to deterioration in the cardiac status and a progressive downhill course in chronic rheumatic heart disease, cardiomyopathies and systemic hypertension.
Treatment: AF of acute onset can be corrected by DC shock after instituting treatment for the underlying condition. This measure is only of temporary benefit in chornic cases.
Digitalisation helps in reducing the heart rate and thereby improves the cardiac output, though the fibrillation is not correctable. Drugs like disopyramide, procainamide, verapamil and amiodarone are capable of converting AF into sinus rhythm when used intravenously. Quinidine also is useful in abolishing atrial fibrillation. This drug is generally given orally, though intravenous preparations are also available.
Anticoagulant therapy has been suggested as a prophylaxis against thromboembolic episodes but this measure is not universally accepted.
© 2014 Funom Theophilus Makama