Premature ventricular beats

Characteristic feature a "long-short" initiating sequence, which occurs as a result of a ventricular premature beat followed by a compensatory pause, which is followed by the first beat of the torsades de pointes. 

It is indicated in prevention of atrial arrhythmia, atrial fibrillation or flutter, paroxysmal supraventricular tachycardia, ventricular premature beats and ventricular tachycardia. 

Ventricular and supraventricular tachycardia (especially those due to re-entry phenomena), atrial fibrillation and flutter (can convert recent-onset fibrillation or flutter to sinus rhythm) Paroxysmal supraventricular tachycardia, atrial or ventricular premature beats, atrial fibrillation, or flutter (slows ventricular rate)... 

Caffeine is derived by extraction of coffee beans, tea leaves, and kola nuts. It is also prepared synthetically. Much of the caffeine of commerce is a by-product of decaffeinized coffee manufacture. The compound is purified by a series of recrystallizations. Caffeine finds use in medicine and in soft drinks. Caffeine is also available as the hydrobromide and as sodium benzoate, winch is a mixture of caffeine and sodium benzoate, containing 47-50% anhydrous caffeine and 50-53% sodium benzoate. This mixture is more soluble in water than pure caffeine. A number of nonprescription (pain relief) drugs contain caffeine as one of several ingiedients. Caffeine is a known cardiac stimulant and in some persons who consume significant amounts, caffeine can produce ventricular premature beats. 

FIGURE 19.4 Relationsliip behA een plasma concentrations of tocainide and suppression of ventricular premature beats (VPBs) for four representative patients. The relationship betwreen VPB frequency and tocainide concentrations shown by the solid curves was obtained from a nonlinear least-squares regression analysis of the data using Equation 19.10. The estimate of n for each patient can be compared with the shape of the tocainide concentration-antiarrhythmic response curve. (Reproduced with permission from Meffin PJ, Winkle RA, Blaschke TF, Fitzgerald J, Harrison DC. Clin Pliarmacol Ther 1977 22 42-57.)... 

These are common after myocardial infarction. Their particular significance is that the R-wave (ECG) of an ectopic beat, developing during the early or peak phases of the T-wave of a normal beat, may precipitate ventricular tachycardia or fibrillation (the R-on-T phenomenon). About 80% of patients with myocardial infarction who proceed to ventricular fibrillation have preceding ventricular premature beats. Lignocaine (lidocaine) is effective in suppression of ectopic ventricular beats but is not often used as its addition increases overall risk. 

Klotz U, Muller-Seydlitz PM, Heimburg P. Lorcainide infusion in the treatment of ventricular premature beats (VPB). Eur J Clin Pharmacol 1979 16(l) l-6. 

ST-segment depression observed in V1-V3 is even more striking in the ventricular premature beats (first QRS in V1-V3). 

Ventricular premature beats, atrial premature beats, atrial arrhythmias, conduction abnormalities all may occur... 

Ruberman W, Weinblatt E, Goldberg JD, et al. Ventricular premature beats and mortality after myocardial infarction. N Engl J Med 1977 297 750-757. 

Serious untoward effects are unusual if dosing is appropriate and the patient is carefully monitored during initial treatment. Levothyroxine replacement in athyrotic hypothyroid patients restores systolic and diastolic left ventricular performance within 2 weeks, and the use of levothyroxine may increase the frequency of atrial premature beats, but not necessarily ventricular premature beats. Excessive doses of... 

C. Differential diagnosis. Rule out the following possible causes of ventricular premature beats, ventricular tachycardia, or ventricular fibrillation ... 

Eight patients with ventricular tachycardia treated with disopyramide 600 mg to 2 g daily had a 54% fall in their serum disopyramide levels (from a mean of 3.99 to 1.82 micrograms/mL) when they were also given phenytoin 200 to 600 mg daily for a week. Two of the patients who responded to disopyramide and underwent Hotter monitoring showed a 53- and 2000-fold increase in ventricular premature beat frequency as a result of this interaction. ... 

Schmidt, G., et al.. Heart-rate turbulence after ventricular premature beats as a predictor of mortality after acute myocardial infarction. Lancet, 1999. 353(9162) p. 1390-6. 

In horses, jugular puke, tachycardia, ventricular premature beats, and S-T elevation Increased amplitude of T wave and shortening of S-T segment similar to hyperkalemic heart failure... 

Premature beats can also originate from the ventricles. Ventricular premature beats look different to the normal QRS complex (have a different morphology). The QRS of the premature beat is usually much wider than the intrinsic rhythm it also usually has no preceding P wave. Figure 6.6 shows a normal beat compared with the ventricular premature beat in Fig. 6.7, which demonstrates the difference in morphology. 

The atria can also be activated retrogradely and sometimes P waves can appear inverted (upside down) merged with the ectopic T wave. The T waves of the ventricular premature beats are usually defected in the opposite direction to the intrinsic rhythm, and also appear odd in appearance. 

Most ventricular premature beats are benign and require no intervention. There are however a small minority of potentially dangerous patterns of premature beat that... 

These are ventricular premature beats that differ in morphology from each other (Fig. 6.11). This is because they often originate from different areas of the ventricle. The presence of these multiform ventricular premature beats can point toward the presence of serious heart disease. 

Fig. 6.9 Three ventricular premature beats occurring together...

Ventricular bigeminy in contrast consists of alternating normal (intrinsic) QRS complexes followed by a regular repeating ventricular premature beat (Fig. 6.14). Ventricular trigeminy like atrial trigeminy occurs after every second QRS complex... 

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