Introduction: It is unclear how aortic stenosis causes angina despite unobstructed coronary arteries. Transcatheter Aortic Valve Implantation (TAVI), permitting the instantaneous abolition of the stenosis, allows quantification of the direct physiological impact of the stenosis independent of associated pathologies such as left ventricular hypertrophy.

Methods: Intracoronary pressure and flow velocity were measured immediately before and after TAVI in six patients with unobstructed coronary arteries. We calculated the intra-coronary diastolic suction wave (the principal accelerator of coronary blood flow). To test physiological reserve to increased myocardial demand, we measured pressure and flow velocity at rest and during pacing at 90 and 120 beats per minute.

Results: Prior to TAVI the basal myocardial suction wave intensity was 2.2±1x10⁻⁵ Wm⁻²s⁻², and increased in magnitude with increasing severity of aortic stenosis (r=0.82, p=0.04). This wave decreased markedly with pacing at higher heart rate (β coefficient=−0.19 x10⁻⁴ Wm⁻²s⁻², p=0.003). After TAVI despite a fall in basal suction wave (2.2±1 v 1.0±0.4x10⁻⁵ Wm⁻²s⁻², p<0.004), there was an immediate improvement in coronary physiological reserve as assessed with pacing (β coefficient=0.12 x10⁻⁴ Wm⁻²s⁻², p=0.014).

Conclusions: In aortic stenosis, the coronary physiological reserve is reversed: instead of increasing with increased myocardial demand, the coronary diastolic suction wave paradoxically decreases. Immediately after TAVI, this physiological reserve returns to a normal positive pattern. This may explain why patients with aortic stenosis suffer from angina despite unobstructed coronaries and the prompt relief of angina after TAVI.