Assessment of mechanical aortic valve prosthesis by means of Doppler echocardiography: what to measure and why?

Cardiac MRI evaluation of hypertrophic cardiomyopathy: left ventricular outflow tract/aortic valve diameter ratio predicts severity of LVOT obstruction

PURPOSE

To evaluate if left ventricular outflow tract/aortic valve (LVOT/AO) diameter ratio measured by cardiac magnetic resonance (CMR) imaging is an accurate marker for LVOT obstruction in patients with hypertrophic cardiomyopathy (HCM) compared to Doppler echocardiography.

MATERIALS AND METHODS

In all, 92 patients with HCM were divided into three groups based on their resting echocardiographic LVOT pressure gradient (PG): <30 mmHg at rest (nonobstructive, n = 31), <30 mmHg at rest, >30 mmHg after provocation (latent, n = 29), and >30 mmHg at rest (obstructive, n = 32). The end-systolic dimension of the LVOT on 3-chamber steady-state free precession (SSFP) CMR was divided by the end diastolic aortic valve diameter to calculate the LVOT/AO diameter ratio.

RESULTS

There were significant differences in the LVOT/AO diameter ratio among the three subgroups (nonobstructive 0.60 ± 0.13, latent 0.41 ± 0.16, obstructive 0.24 ± 0.09, P < 0.001). There was a strong linear inverse correlation between the LVOT/AO diameter ratio and the log of the LVOT pressure gradient (r = -0.84, P < 0.001). For detection of a resting gradient >30 mmHg, the LVOT/AO diameter ratio the area under the receiver operating characteristic (ROC) curve was 0.91 (95% confidence interval [CI] 0.85-0.97). For detection of a resting and/or provoked gradient >30 mmHg, the LVOT/AO diameter ratio area under the ROC curve was 0.90 (95% CI 0.84-0.96).

CONCLUSION

The LVOT/AO diameter ratio is an accurate, reproducible, noninvasive, and easy to use CMR marker to assess LVOT pressure gradients in patients with HCM.

Catheter balloon adjustment of the pulmonary artery band: feasibility and safety

The study aimed to assess the feasibility and safety of increasing pulmonary artery band (PAB) diameter by catheter-based PAB balloon dilation (PABBD). Eight dilations were performed between October 2006 and December 2008. Hemoclips were used to fix PABs surgically in a procedure designed to permit progressive clip dislodgment in a controlled manner. The PABBD resulted in gradual band loosening until the desired physiologic state was achieved. At time of PABBD, the patients had a mean age of 6 months (range 3-14 months) and a mean weight of 5 kg (range 2.6-7.3 kg). The median time from PAB placement until PABBD was 4.5 months (range 1-9 months). The single-balloon technique was used in seven cases (serial dilations in 5 cases) and the double-balloon technique in one case. The PABBDs were successful for all the patients, who experienced a mean saturation increase of 75-89% (P = 0.01) (mean increase of 20%), a mean PAB gradient decrease from 69 to 36 mmHg (P = 0.002) (mean decrease of 49%), and a mean band site diameter increase from 4.1 to 6.1 mm (P = 0.01) (mean increase of 45%). The only complication was transient pulmonary edema in one patient. The PABBD procedure is a feasible and safe method for increasing pulmonary blood flow in a staged manner and may eliminate the need for surgical band removal in some cases.

Mechanical aortic valve prostheses in the small aortic root: Top Hat versus standard CarboMedics aortic valve

BACKGROUND

The purpose of this study was to evaluate outcome in patients with a small aortic root receiving either a standard CarboMedics mechanical aortic valve or a Top Hat CarboMedics valve (CarboMedics, Austin, TX), specifically designed for the small aortic root.

METHODS

Between 1986 and 2006, 316 consecutive patients underwent 19- or 21-mm mechanical aortic valve replacement, receiving either a CarboMedics Top Hat bileaflet valve (n = 56; mean age, 66 +/- 14 years) or a standard CarboMedics aortic valve replacement (n = 260; mean age, 60 +/- 13 years) at our institution based on institutional indications for the choice of type of valve prostheses. Median follow-up time was 83.5 months. We studied survival, valve-related and non-valve-related events, and hemodynamic performance by serial echocardiographic follow-up studies.

RESULTS

In-hospital mortality was 8.9% in the Top Hat group and 10.0% in the standard group (p = 0.354). Five- and ten-year survival in patients in the Top Hat group was 83% and 67%, respectively. Five- and ten-year survival in the standard group was 73% and 59%, respectively (log-rank = 0.331). There were no differences in regard to valve-related and non-valve-related events. Cox regression analysis revealed age (hazard ratio, 1.045; 95% confidence interval, 1.026 to 1.066), previous cardiac surgery (hazard ratio, 1.812; 95% confidence interval, 1.101 to 2.982), additional procedures at the time of valve replacement (hazard ratio, 2.604; 95% confidence interval, 1.651 to 4.108), New York Heart Association class IV (hazard ratio, 3.645; 95% confidence interval, 1.214 to 10.945), and severely impaired left ventricular ejection fraction (hazard ratio, 2.253; 95% confidence interval, 1.289 to 3.941) to be independent predictors of survival.

CONCLUSIONS

Mechanical aortic valve replacement in the small aortic root is associated with substantial perioperative mortality, in particular in the subset of patients requiring additional cardiac surgical procedures. Nevertheless, long-term outcome is satisfying. Because the type of prosthesis does not predict outcome in the multivariate Cox model, we conclude that use of the smaller Top Hat prosthesis can be recommended for the challenging cohort of patients with a small aortic root.

Prosthesis-Patient Mismatch After Aortic Valve Replacement: Impact of Age and Body Size on Late Survival

BACKGROUND

The purpose of this study was to identify patient subgroups in which prosthesis-patient mismatch most influenced late survival.

METHODS

Over a 12-year period, 1,400 consecutive patients underwent bioprosthetic (933 patients) or mechanical (467) aortic valve replacement. Prosthesis-patient mismatch was defined as prosthetic effective orifice area/body surface area less than 0.75 cm2/m2 and was present with 11% mechanical and 51% bioprosthetic valves.

RESULTS

With bioprosthetic valves, prosthesis-patient mismatch was associated with impaired survival for patients less than 60 years old (10-year: 68% +/- 7% mismatch versus 75% +/- 7% no mismatch, p < 0.02) but not older patients (p = 0.47). Similarly, with mechanical valves, prosthesis-patient mismatch was associated with impaired survival for patients less than 60 years old (10-year: 62% +/- 11% versus 79% +/- 4%, p < 0.005) but not older patients (p = 0.26). For small patients (body surface area less than 1.7 m2), prosthesis-patient mismatch did not impact survival with bioprosthetic (p = 0.32) or mechanical (p = 0.71) valves. For average-size patients (body surface area 1.7 to 2.1 m2), prosthesis-patient mismatch was associated with impaired survival with both bioprosthetic (p < 0.05) and mechanical (p < 0.005) valves. For large patients (body surface area greater than 2.1 m2), prosthesis-patient mismatch was associated with impaired survival with mechanical (p < 0.04) but not bioprosthetic (p = 0.40) valves.

CONCLUSIONS

Prosthesis-patient mismatch had a negative impact on survival for young patients, but its impact on older patients was minimal. In addition, although prosthesis-patient mismatch was not important in small patients, prosthesis-patient mismatch negatively impacted survival for average-size patients and for large patients with mechanical valves.

Comparative Evaluation of Small-Size Sorin Slimline and St. Jude HP Heart Valve Prostheses

BACKGROUND

The Sorin Slimline aortic valve prosthesis, a modification of the Sorin Bicarbon valve with increased internal orifice diameter and geometric orifice area, may show improved hemodynamic performance when compared with other previous prosthesis, but so far no comparison study has been reported.

METHODS

Between May 1999 and March 2002, 80 patients (31 to 81 years of age; mean, 65 years) with a small aortic annulus were randomized to undergo aortic valve replacement with either the Sorin Slimline (n = 40) or St. Jude High Performance (n = 40) valve prosthesis. Clinical and echocardiographic Doppler follow-up was performed at 3 to 4 weeks, and 6 and 12 months postoperatively.

RESULTS

One patient died of non-valve-related causes 9 months after operation. Mean and peak pressure gradients at 6 and 12 months in the Sorin Slimline valve were lower than in the St. Jude High Performance valve for both size 19 and 21 mm. Effective orifice area and effective orifice area index were not significantly different. There was a significant (p = 0.0001) reduction in left ventricular mass and left ventricular mass index between preoperative measurements and at 12 months after surgery for both valves, but there was no difference (p = 0.27) between the Sorin Slimline and St. Jude High Performance valve prosthesis at any other follow-up period. Clinical results showed similarly good results with both valves.

CONCLUSIONS

No clinically significant difference in the hemodynamics of both valves was appreciated; patients with a Sorin Slimline valve exhibited statistically significantly lower pressure gradients, but the small differences in effective orifice area and effective orifice area index did not reach significance. A significant left ventricular mass regression was observed with both valve models. Both prostheses provided a satisfactory clinical outcome.

Discrepancy between doppler and catheter measurements of pressure gradients across small-size prosthetic valve

OBJECTIVES

The exact role of pressure gradient across the prosthetic valve estimated from Doppler flow velocity remains controversial. This in-vivo study was designed to assess the actual discrepancy between Doppler and catheter measurements of the pressure gradients for small bileaflet prosthetic valves in the aortic position.

METHODS

Bileaflet prosthetic valves (19 mm-ATS) were implanted into the aortic position in pigs, and pressure gradients across the valves were examined by volume loading under right heart bypass. The pressure gradient obtained by catheter was defined as the conventional peak-to-peak gradient between the left ventricle and aorta. The peak Doppler gradients were calculated from the maximal instantaneous Doppler velocity with the ultrasound probe positioned on the diaphragm at the level of the cardiac apex.

RESULTS

There were strong correlations between pressure gradients and cardiac output. The Doppler gradient was constantly higher than the catheter values, and the resultant discrepancy between Doppler and catheter measurements was directly dependent on cardiac output (y=9.9x+0.6, r2=0.55). For cardiac output > or = 5.0 L/min, the difference between Doppler and catheter gradients reached 40 mmHg, and maximum differences of up to 80 mmHg were observed.

CONCLUSIONS

In view of the presence of striking overestimation of catheter gradient by Doppler measurement, Doppler ultrasound should be used cautiously to assess small-size bileaflet prosthetic valve function with consideration of the patient's hemodynamic state.