Home Monitoring of Patients after Prosthetic Valve Surgery - Experimental Background and First Clinical Attempts

Early detection of mechanical valve dysfunction using a new home monitoring device

BACKGROUND

After heart valve replacement, patients are at risk of complications that are linked to irregular oral anticoagulation therapy. Depending on the type and position of the valve, the complication rate is 3% to 6% per patient-year. This study presents clinical results of a device enabling early detection of prosthetic dysfunction by frequency measurements.

METHODS

Between November 2003 and March 2006, ThromboCheck devices were handed out to 483 patients after mechanical heart valve replacement from six heart centers. In each case, the devices were calibrated for individual patients early postoperatively. Taking control measurements, the device calculated deviations from calibrated frequency and amplitude ranges using a fast Fourier transform and sent a warning message to the display if any relevant changes occurred. This message was taken as cause to determine morphologic correlations of the disturbance using imaging techniques, for example, echocardiography or fluoroscopy (observation period, 550.7 patient-years; median application period, 15.1 months).

RESULTS

Twenty-five true positive, 1 false positive, and no false negative measurements occurred. Eleven patients (44%) received thrombolytic therapy with streptokinase or recombinant tissue-type plasminogen activator, resulting in normalization of the digital frequency analysis. In 4 patients (16%), international normalized ratio levels were adjusted under temporary heparinization therapy. Normalization of the valve sounds were achieved within 3 to 7 days. Seven patients (28%) required reoperation despite lysis therapy. Sensitivity was 100% during the observation period; specificity was 99.8%.

CONCLUSIONS

Digital frequency analysis represents a reasonable addition to the monitoring of patients after artificial heart valve replacement to detect prosthesis-related complications early on.

Occasional single beat regurgitation observed with the medtronic advantage bileaflet heart valve

BACKGROUND

The purpose of this clinical study was to obtain further evidence of the underlying mechanism causing the echocardiographically detected phenomenon of single beat regurgitation in a new bileaflet heart valve. As part of a prospective multicenter trial at our institution, 63 patients received the Advantage bileaflet mechanical heart valve (Medtronic, Minneapolis, Minnesota) in aortic position. During routine follow-up performed at discharge and annually after the operation, intermittent moderate transvalvular regurgitation was detected by echocardiography in 5 patients.

METHODS

Fluoroscopy of leaflet motion (n = 4), invasive blood pressure measurements in the ascending aorta (n = 3) and digital phonocardiography (n = 5) was obtained in the patients showing an intermittent regurgitation during echocardiography.

RESULTS

Valve thrombosis, sutures, or pannus ingrowth impairing valve closure was not detected. Fluoroscopy of leaflet motion showed intermittent incomplete closure of either one of the two leaflets in the same prosthesis. This could be correlated with a distinct diastolic blood pressure drop in the same cardiac cycle. Digital phonocardiography showed pathologic closure sounds in those cycles in which echocardiographically the intermittent regurgitation was observed.

CONCLUSIONS

Some patients with the Medtronic Advantage prosthesis in the aortic position show an intermittent inability of complete valve closure that leads to a single beat transvalvular regurgitation. As thrombotic or other material that might cause a disturbance of leaflet motion could not be detected, and the patients seem not to be exposed to any risk except for some chronic regurgitant volume, we decided not to replace the prostheses.