Impact of heart rate, aortic compliance and stroke volume on the aortic regurgitation fraction studied in an ex vivo pig model

Introduction Drug therapy to reduce the regurgitation fraction (RF) of high-grade aortic regurgitation (AR) by increasing heart rate (HR) is generally recommended. However, chronic HR reduction in HFREF patients can significantly improve aortic compliance and thereby potentially decrease RF. To clarify these contrasts, we examined the influence of HR, aortic compliance and stroke volume (SV) on RF in an ex vivo porcine model of severe AR.Methods Experiments were performed on porcine ascending aorta with aortic valves (n=12). Compliance was varied by inserting a Dacron graft close to the aortic valve. Both tube systems were connected to a left heart simulator varying HR and SV. AR was accomplished by punching a 0.3 cm2 hole in one aortic cusp. Flow, RF, SV and aortic pressure were measured, aortic compliance with transoesophageal ultrasound probes.Results Compliance of the aorta was significantly reduced after Dacron graft insertion (0.55%±0.21%/mm Hg vs 0.01%±0.007%/mm Hg, p<0.001, respectively). With increasing HR, RF was significantly reduced in each steady state of the native aorta (HR 40 bpm: 88%±7% vs HR 120 bpm: 42%±10%; p<0.001), but Dacron tube did not affect RF (HR 40 bpm: 87%±8%; p=0.79; HR 120 bpm: 42%±3%; p=0.86). Increasing SV also reduced RF independent of the stiff Dacron graft.Conclusion Aortic compliance did not affect AR in the ex vivo porcine model of AR. RF was significantly reduced with increasing HR and SV. These results affirm that HR lowering and negative inotropic drugs should be avoided to treat severe AR

Functional interaction of aortic valve and ascending aorta in patients after valve-sparing procedures

Abstract Pressure recovery (PR) is essential part of the post stenotic fluid mechanics and depends on the ratio of EOA/AA, the effective aortic valve orifice area (EOA) and aortic cross-sectional area (AA). In patients with advanced ascending aortic aneurysm and mildly diseased aortic valves, the effect of AA on pressure recovery and corresponding functional aortic valve opening area (ELCO) was evaluated before and after valve-sparing surgery (Dacron graft implantation). 66 Patients with ascending aortic aneurysm (mean aortic diameter 57 +/− 10 mm) and aortic valve-sparing surgery (32 reimplantation technique (David), 34 remodeling technique (Yacoub)) were routinely investigated by Doppler echocardiography. Dacron graft with a diameter between 26 and 34 mm were implanted. EOA was significantly declined after surgery (3.4 +/− 0.8 vs. 2.6 +/− 0.9cm2; p < 0.001). Insertion of Dacron prosthesis resulted in a significant reduction of AA (26.7 +/− 10.2 vs. 6.8 +/− 1.1cm2; p < 0.001) with increased ratio of EOA/AA (0.14 +/− 0.05 vs. 0.40 +/− 0.1; p < 0.001) and pressure recovery index (PRI; 0.24 +/− 0.08 vs. 0.44 +/− 0.06; p < 0.0001). Despite reduction of EOA, ELCO (= EOA corrected for PR) increased from 4.0 +/− 1.1 to 5.0 +/− 3.1cm2 (p < 0.01) with reduction in transvalvular LV stroke work (1005 +/− 814 to 351 +/− 407 mmHg × ml, p < 0.001) after surgery. These effects were significantly better in patients with Yacoub technique than with the David operation. The hemodynamic findings demonstrate a valve-vessel interaction almost entirely caused by a marked reduction in the ascending AA with significant PR gain. The greater hemodynamic benefit of the Yacoub technique due to higher EOA values compared to the David technique was evident and may be of clinical relevance

Functional interaction of aortic valve and ascending aorta in patients after valve-sparing procedures

Pressure recovery (PR) is essential part of the post stenotic fluid mechanics and depends on the ratio of EOA/$A_A$, the effective aortic valve orifice area (EOA) and aortic cross-sectional area ($A_A$). In patients with advanced ascending aortic aneurysm and mildly diseased aortic valves, the effect of $A_A$ on pressure recovery and corresponding functional aortic valve opening area (ELCO) was evaluated before and after valve-sparing surgery (Dacron graft implantation). 66 Patients with ascending aortic aneurysm (mean aortic diameter 57 +/− 10 mm) and aortic valve-sparing surgery (32 reimplantation technique (David), 34 remodeling technique (Yacoub)) were routinely investigated by Doppler echocardiography. Dacron graft with a diameter between 26 and 34 mm were implanted. EOA was significantly declined after surgery (3.4 +/− 0.8 vs. 2.6 +/− 0.9cm$^{2}$; $\it p$ < 0.001). Insertion of Dacron prosthesis resulted in a significant reduction of $A_A$ (26.7 +/− 10.2 vs. 6.8 +/− 1.1cm$^{2}$; $\it p$ < 0.001) with increased ratio of EOA/$A_A$ (0.14 +/− 0.05 vs. 0.40 +/− 0.1; $\it p$ < 0.001) and pressure recovery index (PRI; 0.24 +/− 0.08 vs. 0.44 +/− 0.06; $\it p$ < 0.0001). Despite reduction of EOA, ELCO (= EOA corrected for PR) increased from 4.0 +/− 1.1 to 5.0 +/− 3.1cm$^{2}$ ($\it p$ < 0.01) with reduction in transvalvular LV stroke work (1005 +/− 814 to 351 +/− 407 mmHg × ml, $\it p$ < 0.001) after surgery. These effects were significantly better in patients with Yacoub technique than with the David operation. The hemodynamic findings demonstrate a valve-vessel interaction almost entirely caused by a marked reduction in the ascending $A_A$ with significant PR gain. The greater hemodynamic benefit of the Yacoub technique due to higher EOA values compared to the David technique was evident and may be of clinical relevance