BackgroundAlthough the use of physical signs for the diagnosis of ventricular tachycardia (VT) was described in the early 1900s, their value in this role has never been systematically assessed.Methods and ResultsUsing a blinded, randomized protocol, we examined the ability of 26 clinicians to detect ventriculoatrial (VA) dissociation during cardiac pacing in 21 patients with both atrial and ventricular pacing wires in situ after successful ablation of accessory pathways. In protocol 1 (10 patients), pacing was randomized to either ventricular pacing alone (simulating VT) or to atrioventricular sequential pacing (simulating supraventricular tachycardia or VT with intact VA conduction) at rates of 150 or 180 beats per minute. Each patients was examined by four clinicians blinded to the pacing mode. Clinicians were asked to make a diagnosis of “VA association” or “VA dissociation” after examining the patient for variability of the arterial pulse, jugular venous pulse (JVP), and first heart sound. In protocol 2 (11 patients), randomization of pacing mode was performed between examination of each of the three physical signs so that the value of each sign was assessed individually. In protocol 1, a diagnosis of VA dissociation (VT) was made in 21 of 40 observations, with a specificity of 75%, sensitivity of 70%, and a positive predictive value (PPV) of 71%. In protocol 2, from a total of 132 observations (44 for each sign), the sensitivity, specificity, and PPV for a diagnosis of VT were as follows: arterial pulse, 61%, 71%, 70%; JVP, 96%, 75%, 82%; and first heart sound, 58%, 100%, 100%.ConclusionsIt is concluded that, in patients with a regular tachycardia of uncertain origin, clinically detectable variations in the first heart sound and JVP are highly specific and sensitive indicators, respectively, of a diagnosis of VT. Assessment of the arterial pulse is of little value in this role.