Medtronic Mosaic porcine bioprosthesis: assessment of 12-year performance.

BACKGROUND: The Mosaic porcine bioprosthesis (Medtronic, Inc, Minneapolis, Minn) was approved in 2000 by the US Food and Drug Administration. Clinical performance was evaluated in 6 centers. METHODS: From 1994 to 2000, 797 patients (mean age 69 years) had aortic valve replacement (AVR) and 232 (mean 67 years) had mitral valve replacement (MVR). Concomitant coronary artery bypass grafting was performed with aortic valve replacement (45.4%) and mitral valve replacement (43.5%). Mean follow-ups were 7.5 years for aortic position and 7.3 years for mitral position. RESULTS: Early mortalities were 2.8% for AVR and 3.0% for MVR. Late mortalities were 4.2%/patient-year for AVR and 5.1%/patient-year for MVR. Overall 12-year survivals were 55.8% ± 3.7% for AVR and 43.9% ± 7.4% for MVR. Twelve-year freedoms from valve-related mortality were 87.1% ± 3.1% for AVR and 82.5% ± 7.7% for MVR. Twelve-year freedoms from reoperation were 84.0% ± 3.3% for AVR and 82.5% ± 7.5% for MVR. Freedoms from structural valve deterioration (SVD) by explant reoperation at 12 years for AVR were 93.3% ± 2.6% for patients at least 60 years old and 75.9% ± 9.3% for patients younger than 60 years. Freedoms from SVD by explant reoperation at 10 years for MVR were 95.3% ± 7.8% for patients at least 70 years old and 84.0% ± 9.3% for patients younger than 70 years. Hemodynamic performance data at 1 year for AVR (sizes 21-27 mm) were mean systolic gradient range 13.7 ± 4.8 to 10.3 ± 3.2 mm Hg and effective orifice area range 1.5 ± 0.3 to 2.5 ± 0.4 cm(2). For MVR (sizes 25-31 mm), data were mean diastolic gradient range 6.7 ± 1.7 to 3.7 ± 0.9 mm Hg and effective orifice area range 1.9 ± 0.3 to 2.4 ± 0.6 cm(2). CONCLUSIONS: Overall performance of Mosaic porcine bioprosthesis to 12 years is satisfactory. Freedoms from SVD by explant reoperation were most satisfactory for aortic position in patients at least 60 years old and mitral position in patients at least 70 years old. Overall actuarial freedom from SVD by explant reoperation is encouraging for patients with MVR.

Phase I and Phase II oxygen uptake kinetics during atrioventricular dyssynchrony in chronotropically competent pacemaker patients.

OBJECTIVE: To elucidate the effects of atrioventricular (AV) dyssynchrony on phase I and phase II oxygen uptake (V(O2)) kinetics in chronotropically competent pacemaker patients during exercise of an intensity comparable to activities of daily living. DESIGN: Blinded patients completed sub-ventilatory threshold (VT) work rate (WR) cycle ergometry exercise in random order during asynchronous AV pacing (AV OFF) and synchronous AV pacing. SETTING: Tertiary care hospital in a major city. SUBJECTS: Six chronotropically competent male pacemaker patients (mean [+/- SD] age, 68 +/- 10 years) with high-degree AV block and varying cardiac histories. RESULTS: The phase I and phase II V(O2) amplitude response and gain (deltaV(O2)/WR ratio) were lower (p < 0.05) and the time course of phase II was slower (p < 0.05) during AV OFF; however, the O2 deficit was similar (p > 0.05) across pacing modes. The stroke volume index (SVI) was consistently lower (p < 0.05) during AV OFF pacing and was significantly correlated with the time course of phase II V(O2). A significant compensatory amplitude response in heart rate (HR) was observed in addition to a higher (p < 0.05) deltaHR/V(O2) ratio during AV OFF. Ventilatory responses were consistent with ventilatory-perfusion mismatching and perceived exertion was higher during asynchronous pacing. CONCLUSION: This study demonstrated that the contribution of SVI affects V(O2) kinetics and underscores the importance of the atrial contribution to ventricular filling and, consequently, to metabolic and hemodynamic responses. This study supports the theory of an O2 transport limitation and further implicates SV as a potential limiting factor during sub-VT exercise intensities that are comparable to those encountered in activities of daily living.

Impact of a right ventricular impedance sensor on the cardiovascular responses to exercise in pacemaker dependent patients.

BACKGROUND: The evaluation of the heart rate (HR) response to exercise is important for the assessment of the rate response algorithm of sensor-controlled pacemakers. This study examined the effects of a right ventricular impedance sensor driven pacemaker on the cardiovascular responses to incremental exercise in pacemaker dependent patients. METHODS: Twelve patients (70.5 +/- 9.5 years; 5 Females: 7 Males) implanted with an Inos(2+) closed loop stimulation (CLS) pacemaker were compared to 12 healthy age and sex matched controls (70.6 +/- 4.8 years). All subjects performed the chronotropic assessment exercise protocol (CAEP). Variables of interest included HR, cardiac output (Q), oxygen uptake (VO2) and blood pressure (BP). Data were analyzed at rest, throughout exercise and during recovery. Furthermore, patient chronotropic responses were compared to a reference chronotropic response slope for aerobic exercise. RESULTS: There were no differences between groups for HR or Q response throughout exercise. At peak exercise, VO2 (mL x kg(-1) x min(-1)) was higher for the controls (p < 0.05). The patient chronotropic response slope was comparable to the CAEP reference slope from rest to both the anaerobic threshold (AT) and peak exercise. During recovery, no differences were observed between the groups for any parameters or for the HR decay slopes. CONCLUSION: Up to the anaerobic threshold, the right ventricular impedance sensor driven pacemaker delivered a pacing rate that contributed to an overall cardiovascular response similar to that observed in healthy age matched subjects.

The mosaic valve clinical performance at seven years: results from a multicenter prospective clinical trial.

BACKGROUND AND AIM OF THE STUDY: The Mosaic valve is a third-generation stented porcine bioprosthesis built upon the historical durability of the Hancock II valve in an attempt to improve hemodynamic performance and durability. METHODS: This multicenter trial was prospective and non-randomized in design. Between February 1994 and October 1999, six centers following a common study protocol enrolled 797 patients (mean age 70 years: range: 21-88 years) who underwent aortic valve replacement (AVR), and 232 patients (mean age 68 years; range: 17-84 years) who underwent mitral valve replacement (MVR). The cumulative follow up was 3,442 patient-years (pt-yr) for AVR (mean 4.3 years; maximum 8 years), and 870 pt-yr for MVR (mean 3.7 years; maximum 7 years). Follow up was complete for 95% of AVR patients, and for 97% of MVR patients. RESULTS: The mean gradient and calculated effective orifice area average across all valve sizes remained stable at one, four and six years. Freedom from valve-related adverse events (mean +/- SE) at one, four and seven years after AVR were, respectively: Antithromboembolic-related hemorrhage (ARH) 97.0 +/- 0.6, 95.6 +/- 0.9, and 94.6 +/- 5.1%; primary hemolysis 100, 100, and 100%; and structural valve deterioration (SVD) 100, 100 and 100%. Freedom at one, four and seven years after MVR were: ARH 96.9 +/- 1.2, 95.6 +/- 2.0, and 95.6 +/- 7.6%; primary hemolysis 100, 100, and 100%; and SVD 100, 100, and 100%. CONCLUSION: These mid-term results demonstrate the clinical safety and excellent performance of the Mosaic valve. Continued follow up will determine if this new-design, third-generation bioprosthesis will provide increased durability.

Impact of adaptive rate pacing controlled by a right ventricular impedance sensor on cardiac output in response to exercise.

This study examined the effects of adaptive rate pacing controlled by closed-loop right ventricular impedance sensing on exercise hemodynamics. Twelve patients in whom Biotronik INOS2+ pacemakers had been implanted 4-6 weeks earlier participated in the study. All patients completed two graded, symptom-limited exercise tests. The pacemaker was programmed to DDDR with an upper rate limit of 75-85% of the age-predicted maximum heart rate and a lower rate limit of 45-60 ppm. Heart rate was recorded continuously. An average of 5 beats during the last 10 seconds of each exercise stage was used in the analysis. Oxygen uptake (VO2) was measured using open circuit spirometry. The VO2 values from the final 15 seconds of each exercise stage were used for analysis. Stroke volume and cardiac output were measured during the last minute of each stage using impedance cardiography. The test-retest reliability of heart rate and cardiac output responses to graded exercise was assessed using repeated measures analysis of variance, for which the reliability coefficients were r = 0.993 and r = 0.954, respectively (P < 0.01). There were significant correlations (P < 0.01) between VO2 and heart rate and between VO2 and cardiac output, with correlation coefficients of r = 0.907 and r = 0.824, respectively. This method of adaptive rate pacing produced reliable, positive hemodynamic responses to graded exercise on a test-retest basis.

Right ventricular wall hematoma due to thrombolytic therapy presenting as cardiac tamponade: a case report and review of literature.

Intramyocardial hematoma is an uncommon condition, most often occurring after myocardial infarction or chest trauma. A 54-year-old male patient with a large right ventricular wall hematoma who presented with cardiac tamponade three days after acute inferoposterior myocardial infarction and thrombolysis is described. This is the first report of intramyocardial hematoma related to thrombolytic therapy. The patient was managed conservatively with complete resolution of the right ventricular hematoma.