"Stable" ventricular tachycardia is not a benign rhythm : insights from the antiarrhythmics versus implantable defibrillators (AVID) registry.

BACKGROUND: Sustained ventricular tachycardia (VT) can be unstable, can be associated with serious symptoms, or can be stable and relatively free of symptoms. Patients with unstable VT are at high risk for sudden death and are best treated with an implantable defibrillator. The prognosis of patients with stable VT is controversial, and it is unknown whether implantable cardioverter-defibrillator therapy is beneficial. METHODS AND RESULTS: Screening for the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial identified patients with both stable and unstable VT. Both groups were included in a registry, and their clinical characteristics and discharge treatments were recorded. Mortality data were obtained through the National Death Index. The mortality in 440 patients with stable VT tended to be greater than that observed in 1029 patients presenting with unstable VT (33.6% versus 27.6% at 3 years; relative risk [RR]=1.22; P:=0.07). After adjustment for baseline and treatment differences, the RR was little changed (RR=1.25, P:=0.06). CONCLUSIONS: Sustained VT without serious symptoms or hemodynamic compromise is associated with a high mortality rate and may be a marker for a substrate capable of producing a more malignant arrhythmia. Implantable cardioverter-defibrillator therapy may be indicated in patients presenting with stable VT.

Ventricular tachycardia as default diagnosis in broad complex tachycardia.

In the differential diagnosis of broad-complex tachycardia, the most important decision is whether or not the tachycardia is ventricular, since this type carries the worst prognosis. However, the rules for a diagnosis of ventricular tachycardia are so complex that they are not satisfied in many cases, and the default diagnosis, supraventricular tachycardia, is erroneously accepted. We sought to reverse this strategy; unless simple rules for a positive diagnosis of supraventricular tachycardia were satisfied, ventricular tachycardia was diagnosed by default. The criterion for a diagnosis of supraventricular tachycardia was electrocardiographic (ECG) findings typical of bundle branch block (left = rS or QS wave in leads V1 and V2, delay to S wave nadir < 70 ms, and R wave and no Q wave in lead V6; right = rSR' wave in lead V1 and an RS wave in lead V6, with R wave height greater than S wave depth). Twelve-lead ECGs were done for 102 consecutive patients with broad-complex tachycardia (QRS width > 110 ms). Two observers, who were unaware of definitive diagnoses validated by electrophysiology, by our diagnostic rules made correct diagnosis of ventricular tachycardia in 63 and 62 of 69 patients, respectively, and correct diagnoses of supraventricular tachycardia in 28 and 22 of 33 patients (sensitivity for ventricular tachycardia 90% and 91%, specificity 67% and 85%). One observer then sought independent P waves in cases diagnosed as supraventricular tachycardia; sensitivity for the diagnosis of ventricular tachycardia rose to 96%, with a specificity of 64%. These criteria, which require only knowledge of typical bundle branch block patterns, were highly sensitive for the important diagnosis of ventricular tachycardia.

Effect of carbohydrate rich versus fat rich loads on gas exchange and walking performance in patients with chronic obstructive lung disease.

BACKGROUND: High calorie intakes, especially as carbohydrate, increase carbon dioxide production (VCO2) and may precipitate respiratory failure in patients with severe pulmonary disease. Energy obtained from fat results in less carbon dioxide and thus may permit a reduced level of alveolar ventilation for any given arterial blood carbon dioxide tension (PaCO2). METHODS: Ten patients with stable severe chronic obstructive lung disease underwent a six minute walk before and 45 minutes after taking 920 kcal of a fat rich drink, an isocalorific amount of a carbohydrate rich drink, and an equal volume of a non-calorific control liquid on three separate days, in a double blind randomised crossover study. Borg scores of the perceived effort to breathe were measured at the beginning and end of each six minute walk. Minute ventilation (VE2), VCO2, oxygen consumption (VO2), respiratory quotient (RQ), arterial blood gas tensions, and lung function were measured before and 30 minutes after each test drink. RESULTS: Baseline measurements were similar on all three test days and the non-calorific control drink resulted in no changes in any of the measured variables. The carbohydrate rich drink resulted in significantly greater increases in VE, VCO2, VO2, RQ, PaCO2, and Borg score and a greater fall in the distance walked in six minutes than the fat rich drink (mean fall after carbohydrate rich drink 17 m v 3 m after fat rich drink and the non-calorific control). The increase in VCO2 correlated significantly with the decrease in six minute walking distance and the increase in Borg score after the carbohydrate rich drink. The only significant change after the fat rich drink when compared with the non-calorific control was an increase in VCO2. CONCLUSIONS: Comparatively small changes in the carbohydrate and fat constitution of meals can have a significant effect on VCO2, exercise tolerance, and breathlessness in patients with chronic obstructive lung disease.