Hemodynamic and functional assessment of mechanical aortic valves using combined echocardiography and multidetector computed tomography

Background

Limitations are found in the ability of transthoracic echocardiography to evaluate mechanical aortic valve replacements (AVR). We evaluated the ability of combined echocardiography and computed tomography (CT) to enhance the hemodynamic and functional evaluation of AVR.

Methods

We performed a retrospective evaluation of 41 consecutive patients with AVR (27 bileaflet, 14 single disc) and both transthoracic echocardiography and 64-detector electrocardiographic-gated CT. Each study was interpreted by 2 independent, blinded readers. The effective orifice area was compared with the corrected energy-loss coefficient area and the geometric orifice area. Patients with an elevated mean pressure gradient (>15mm Hg) were assessed for potential abnormal findings, including patient–prosthesis mismatch, elevated cardiac index, valve dysfunction, significant regurgitation, or pressure recovery effect.

Results

Significant differences (P<0.05) and moderate-to-high correlations (r=0.55–0.98) were observed between the effective orifice area (2.2±0.8cm²), corrected energy-loss coefficient area (3.0±1.5cm²), and geometric orifice area (3.6±0.9cm²). At least one abnormality was observed in 7 of 25 patients with normal gradients and in 14 of 16 patients with elevated gradients (P<0.001). In 16 patients with elevated mean pressure gradient, a potential cause could be determined in 4 with echocardiography alone and in 14 patients with combined echocardiography and CT (P=0.001).

Conclusion

CT aids in the interrogation of prosthetic valve function, enhancing evaluation for patient prosthesis mismatch, and correction for pressure recovery by the corrected energy-loss coefficient. CT is additive to the assessment of mechanical AVR with transthoracic echocardiography, and the combination permits a more complete assessment of both AVR function and hemodynamics.

Keywords: Aortic valve, Echocardiography, Heart valve disease, Heart valve prosthesis, Spiral computed tomography