Impact of Aortic Valve Stenosis on Coronary Hemodynamics and the Instantaneous Effect of Transcatheter Aortic Valve Implantation

Abstract

Background— Aortic valve stenosis (AS) induces compensatory alterations in left ventricular hemodynamics, leading to physiological and pathological alterations in coronary hemodynamics. Relief of AS by transcatheter aortic valve implantation (TAVI) decreases ventricular afterload and is expected to improve microvascular function immediately. We evaluated the effect of AS on coronary hemodynamics and the immediate effect of TAVI. Methods and Results— Intracoronary pressure and flow velocity were simultaneously assessed at rest and at maximal hyperemia in an unobstructed coronary artery in 27 patients with AS before and immediately after TAVI and in 28 patients without AS. Baseline flow velocity was higher and baseline microvascular resistance was lower in patients with AS as compared with controls, which remained unaltered post-TAVI. In patients with AS, hyperemic flow velocity was significantly lower as compared with controls (44.5±14.5 versus 54.3±18.6 cm/s; P =0.04). Hyperemic microvascular resistance (expressed in mm Hg·cm·s −1 ) was 2.10±0.69 in patients with AS as compared with 1.80±0.60 in controls ( P =0.096). Coronary flow velocity reserve in patients with AS was lower, 1.9±0.5 versus 2.7±0.7 in controls ( P <0.001). Improvement in coronary hemodynamics after TAVI was most pronounced in patients without post-TAVI aortic regurgitation. In these patients (n=20), hyperemic flow velocity increased significantly from 46.24±15.47 pre-TAVI to 56.56±17.44 cm/s post-TAVI ( P =0.003). Hyperemic microvascular resistance decreased from 2.03±0.71 to 1.66±0.45 ( P =0.050). Coronary flow velocity reserve increased significantly from 1.9±0.4 to 2.2±0.6 ( P =0.009). Conclusions— The vasodilatory reserve capacity of the coronary circulation is reduced in AS. TAVI induces an immediate decrease in hyperemic microvascular resistance and a concomitant increase in hyperemic flow velocity, resulting in immediate improvement in coronary vasodilatory reserve.

Quantitative Assessment of Coronary Microvascular Function

“…110, 112, 113 In many of these myocardial disease states the impaired coronary flow carries prognostic information, 103, 107, 118 and improvements in coronary flow parameters have been described after treatment of the underlying cardiac disease. 104, 105, 114, 116 Reduced CFR has been also identified in patients with chronic kidney disease and CFR has been shown to have a significant positive correlation with GFR in these patients. 120 Additionally, global CFR was shown to be independently associated with all-cause mortality in dialysis dependent end stage renal disease patients.…”

Regression of left ventricular hypertrophy provides an additive physiological benefit following treatment of aortic stenosis: Insights from serial coronary wave intensity analysis

“…6 The reason for this appears twofold with some studies suggesting it is due to a fall in the resting coronary flow velocity 1,4 and others showing an increase in hyperaemic flow velocity. 6 The reason for this appears twofold with some studies suggesting it is due to a fall in the resting coronary flow velocity 1,4 and others showing an increase in hyperaemic flow velocity.…”

“…This implies that under these extreme conditions a series of physiological changes have occurred to preserve coronary efficiency (such as a reduction in basal coronary resistance 6 ) and optimize ventricular-coronary coupling. This implies that under these extreme conditions a series of physiological changes have occurred to preserve coronary efficiency (such as a reduction in basal coronary resistance 6 ) and optimize ventricular-coronary coupling.…”

“…6 The reason for this appears twofold with some studies suggesting it is due to a fall in the resting coronary flow velocity 1,4 and others showing an increase in hyperaemic flow velocity. 3,6 Certainly, relative high coronary flow rates are recognized in severe aortic stenosis, 14 particularly when symptomatic 15 and a reduction in resting coronary flow velocity has been seen when measured using intracoronary Doppler wires 1 or transthoracic echocardiography 4 before and after SAVR. Here, we have shown a similar high coronary flow velocity with severe aortic stenosis and have demonstrated that this is associated with a large BDW.…”

“…Two dominant structural changes occur in aortic stenosis, that of an increasingly stenotic outflow tract along with the development of left ventricular hypertrophy (LVH). Whilst many investigative modalities have shown the effect of aortic valve intervention on coronary haemodynamics, [1][2][3][4][5][6] the individual effect of LVH regression is yet to be directly demonstrated using serial post-operative measurements despite the positive impact this change has in a non-valvular setting. 7 Whilst some indirect approaches have suggested that such intervention-driven LVH regression does not markedly influence coronary physiology, 2 recent data have shown that these structural changes result in more favourable clinical outcomes 8 implying at least a moderate impact on the coronary axis.…”