From the Guidelines
The expected valve gradient for a #19 mechanical aortic valve replacement (AVR) is typically less than 20 mmHg for mean gradient, as indicated by the European Association of Cardiovascular Imaging guidelines 1.
Key Considerations
- The guidelines provide a framework for assessing prosthetic heart valve obstruction, including qualitative, semi-quantitative, and quantitative parameters 1.
- For a #19 mechanical AVR, a mean gradient of less than 20 mmHg is considered normal, while a mean gradient of 20-34 mmHg may indicate possible obstruction, and a mean gradient of 35 mmHg or higher may indicate significant obstruction 1.
- It is essential to consider the effective orifice area of the prosthetic valve, which can be affected by the size of the valve and the patient's body surface area 1.
Clinical Implications
- Patient-prosthesis mismatch may occur with smaller valve sizes, such as #19, particularly in patients with larger body surface areas, leading to increased resistance to blood flow 1.
- During follow-up echocardiography, serial measurements should be compared to detect potential valve dysfunction, rather than relying solely on absolute values 1.
- Gradients may increase with higher cardiac output states, such as exercise or infection, and a significant increase in gradients from baseline (typically >10 mmHg increase in mean gradient) warrants further evaluation to rule out complications such as valve thrombosis or pannus formation 1.
From the Research
Expected Valve Gradients for #19 Mechanical AVR
- The expected valve gradients for a #19 mechanical aortic valve replacement (AVR) are not directly stated in the provided studies 2, 3, 4, 5, 6.
- However, the studies discuss the concept of patient-prosthesis mismatch (PPM) and its impact on outcomes after AVR.
- PPM is defined as an indexed effective orifice area (iEOA) <0.65 cm2/m2 for aortic valve prostheses 2, 4.
- The incidence of PPM varies widely, ranging from 8% to almost 80% in individual studies 2.
- Severe PPM is associated with higher rates of perioperative stroke and renal failure, and lack of left ventricular mass regression 2.
- The study by 5 evaluated the incidence of mismatch and its influence on early and late results in aortic valve replacement using prosthesis No 19, but does not provide specific valve gradient values.
- The impact of PPM on outcomes after AVR depends on age at operation, with PPM having a greater impact on younger patients with left ventricular dysfunction 6.
Valve Gradient Considerations
- High prosthetic valve velocity or gradient and a small calculated effective orifice area may indicate PPM 2.
- Re-intervention may be considered if symptoms persist and are unresponsive to medical therapy, but the decision needs to consider the available options to relieve PPM and whether expected benefits justify the risk of intervention 2.
- Accurate assessment of the patient's annular size and indexing the effective orifice area (EOA) of the prosthesis to patient's body surface area (BSA) at the time of prosthesis implantation are important steps to preventing future PPM 4.