AimsFactors underlying clinical tolerance and hemodynamic consequences of monomorphic sustained ventricular tachycardia (VT) need to be clarified.MethodsIntra-arterial pressures (IAP) during VT were collected in patients admitted for VT ablation and correlated to clinical, ECG and baseline echocardiographical parameters.Results114 VTs from 58 patients were included (median 67 years old, 81% ischemic heart disease, median left ventricular ejection fraction 30%). 61 VTs were untolerated needing immediate termination (54%). VT tolerance was tightly linked to the evolution of IAPs. Faster VT rates (p<0.0001), presence of resynchronization therapy (p = 0.008), previous anterior myocardial infarction (p = 0.009) and more marginally larger baseline QRS duration (p = 0.1) were independently associated with VT tolerance. Only an inferior myocardial infarction was more often present in patients with only tolerated VTs vs patients with only untolerated VTs in multivariate analysis (OR 3.7, 95% CI 1.4–1000, p = 0.03). In patients with both well-tolerated and untolerated VTs, a higher VT rate was the only variable independently associated with untolerated VT (p = 0.02). Two different patterns of hemodynamic profiles during VT could be observed: a regular 1:1 relationship between electrical (QRS) and mechanical (IAP) events or some dissociation between both. VT with the second pattern were more often untolerated compared to the first pattern (78% vs 29%, p<0.0001).ConclusionThis study helps to explain the large variability in clinical tolerance during VT, which is clearly related to IAP. VT tolerance may be linked to resynchronization therapy, VT rate, baseline QRS duration and location of myocardial infarction.