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At least 19 recordsLinked to original sources
PubMed2005

The management of mechanical hearts.

Mechanical ventricular assist devices are now approved as destination therapy for terminal heart failure. It is the purpose of this review to discuss the physiology of this technology that is considered in outpatient care. The currently available pulsatile devices are solely dependent of preload volume, and when placed in the automatic mode, can maintain physiologic cardiac outputs with exercise. However, because of their dependence on preload volume, there are unique physiologic consequences; device bradycardia represents volume depletion, device tachycardia reflects volume overload. The differential diagnosis of left ventricular assist device dysfunction includes native right ventricular failure, native left ventricular recovery, or other technical considerations. The management of biventricular mechanical support will be discussed, as well as arrhythmia management and the role of echocardiographic assessment in this unique patient population. Expertise in outpatient management of such devices is now a requisite for subspecialists in heart failure. In the future, technical innovations may simplify management for professionals, patients and their families.

Arrhythmias, Cardiac↗
PubMedDate not supplied

Platelets are deposited early post-operatively on the leaflet of a mechanical heart valve in sheep without post-operative anticoagulants or antiplatelet agents. A scanning electron microscopic observation of the pyrolytic carbon surface in a mechanical heart valve.

Pyrolytic carbon has been used for mechanical heart valves as a thromboresistant, wear resistant, and fatigue resistant material. Thrombosis and thromboembolism, however, remain major mechanical heart valve associated complications and may frequently occur during the early post-operative period. In depth morphologic studies on blood-pyrolytic carbon surface interactions are limited. The purpose of this study was to evaluate the blood compatibility of the pyrolytic carbon surface of St. Jude Medical mechanical heart valves that were implanted in the mitral position of sheep without the administration of post-operative anticoagulants or antiplatelet agents for 2, 4, and 6 weeks. Almost the entire leaflet and orifice ring surfaces were observed by scanning electron microscopy. Although the surfaces appeared clean macroscopically, when observed by electron microscopy, the surface were mottled, mainly by solitary platelets and aggregations. There were only a few leukocytes or red blood cells observed. No fibrin clots were observed on the leaflets. The density of platelet deposition was higher in the vicinity of the pivots and near the edges of the leaflets. The sizes of the platelet aggregations decreased with longer duration. The outer surfaces of the pivot guards were covered by various amounts of deposition composed of platelet aggregations and thrombi. Thus, the administration of antiplatelet agents is recommended during the early post-operative period after mechanical heart valve implantation.

Animals↗
PubMed1984

Effects of intraaortic balloon pumping on acute myocardial infarction in 64 cases of cardiogenic shock, severe heart failure and mechanical heart failure.

Of the patients treated in the CCU of Nippon Medical School for acute myocardial infarction in the past 5 years and 8 months, 44 with cardiogenic shock, 11 with severe heart failure, 7 with ventricular septal perforation and 2 with mitral regurgitation were treated by IABP. The peak effect of IABP on the hemodynamics of patients with cardiogenic shock was noted 24 hours after starting on IABP. When hemodynamics were compared between surviving and dead groups, there was a significant difference in stroke volume index between the two groups. When left ventricular function was compared between them, it was suggested that patients whose left ventricular function does not respond to IABP for 48 hours or longer are more likely to die than responders. Twenty-four of 44 patients became independent of IABP, but no more than 13 patients (30%) survived for 6 months or longer. Isosorbide dinitrate (ISDN) was combined with IABP in 7 patients who had a persistence of heart failure in spite of IABP. Combination therapy with IABP and ISDN elicited a significant increase in cardiac index, a significant decrease in pulmonary capillary wedge pressure, mean pulmonary arterial pressure and total peripheral resistance and a pronounced improvement in left ventricular function, and all 7 patients became independent of IABP. In the patients with acute myocardial infarction complicated with ventricular septal perforation, the mean systolic arterial pressure was 87.7 +/- 8.3 mmHg, mean pulmonary capillary wedge pressure, 20.3 +/- 7.4 mmHg and pulmonary-to-systemic flow ratio, 3.12 +/- 0.95 before starting on IABP. When the hemodynamics at 3 hours of IABP were compared to the pre-IABP values, the right atrial pressure, pulmonary capillary wedge pressure and pulmonary-to-systemic flow ratio had a tendency to decline, but the changes were not statistically significant, except for the peak arterial pressure which showed a significant elevation at 3 hours of IABP. Three of the 7 patients became dependent on IABP, and 2 of the 3 patients were saved by emergency operation.

Aged↗
PubMed2000

[Advances and perspectives in mechanical heart assist].

Mechanical circulatory support devices were first developed to permanently replace the failing heart. Today, however, the majority of these devices are used as a mechanical bridge in patients awaiting heart transplantation. With this indication, important information on using mechanical assist devices has been assembled. We present our experience, which has been gained since 1987 in the area of patient selection, post-implant patient care and device maintenance. More than 450 patients have since been implanted with assist devices at our institution. Mechanical circulatory support may not only lead to recovery from secondary organ failure, but also to myocardial remodeling and recovery of the heart function in some patients. Additionally we report our experience with a newly developed implantable axial flow pump and discuss the possibility and costs of permanent support in some patients.

Adult↗
PubMed2003

Closing behavior of the mechanical heart valve in a total artificial heart.

Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. The cause of cavitation in mechanical heart valve was investigated in both 25-mm Björk-Shiley and 25-mm Medtronic Hall valves. The closing events of these valves in the mitral position were simulated in an electrohydraulic total artificial heart with a stroke volume of 85 ml. The tests were conducted under physiologic pressures at heart rates of 60, 70, 80, and 90 beats/min with cardiac outputs of 4.5, 5.5, 6.4, and 7.5 l/min, respectively. The disk closing behavior was measured by a laser displacement sensor. The closing behaviors were investigated under various atrial and aortic pressures. In both valves, the duration of closing decreased with an increase in the cardiac output. The greater the amount of atrial pressure, the shorter the closing duration of both valves. The maximum closing velocity of the Medtronic Hall monostrut valve ranged from 0.8 to 0.9 m/s, and that of the Björk-Shiley monostrut valve ranged from 0.73 to 0.78 m/s. In both valves, the maximum closing velocities were less than the reported cavitation thresholds. This suggests that there should be no possibility of occurrence of cavitation in an electrohydraulic total artificial heart with mechanical heart valve.

Biomechanical Phenomena↗
PubMedDate not supplied

Diamond-like carbon coating and plasma or glow discharge treatment of mechanical heart valves.

All mechanical heart valves (MHV) are thrombogenic. Application of surface modification technology to reduce the incidence of thrombus formation on MHV is a novel undertaking. This requires collaboration within the bioengineering and cardiothoracic surgery fields. From reviewing results of recent and past investigations, and our own preliminary study with diamond-like carbon coating (DLC) and plasma or glow discharge treatment (GDT) of MHV, we identify and discuss several potentially beneficial effects that may reduce the extent of valve-related thrombogenesis by surface modification. DLC and GDT may affect the surfaces of MHV in many ways, including cleaning of organic and inorganic debris, generating reactive and functional groups on the surface layers without affecting their bulk properties, and making the surfaces more adherent to endothelial cells and albumin and less adherent to platelets. These different effects of surface modification, separately or in combination, may transform the surfaces of MHV to be more thromboresistant in the vascular system.

Animals↗
PubMed2000

A new method for quantitative evaluation of perceived sounds from mechanical heart valve prostheses.

Closing clicks from mechanical heart valve prostheses are transmitted to the patient's inner ear mainly in two different ways: as acoustically transmitted sound waves, and as vibrations transmitted through bones and vessels. The purpose of this study was to develop a method for quantifying what patients perceive as sound from their mechanical heart valve prostheses via these two routes. In this study, 34 patients with implanted mechanical bileaflet aortic and mitral valves (St Jude Medical and On-X) were included. Measurements were performed in a specially designed sound insulated chamber equipped with microphones, accelerometers, preamplifiers and a loudspeaker. The closing sounds measured with an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the 'real-time' clicks he or she perceived directly from his or her valve. In this way the feedback sound energy includes both the air- and the bone-transmitted energies. Sound pressure levels (SPLs) were quantified both in dB(A) and in the loudness unit sone according to ISO 532B (the Zwicker method). The mean air-transmitted SPL measured close to the patient's ear was 23 +/- 4 dB(A). The mean air- and bone-transmitted sounds and vibrations were perceived by the patients as an SPL of 34 +/- 5 dB(A). There was no statistically significant difference in the perceived sound from the two investigated bileaflet valves, and no difference between aortic and mitral valves. The study showed that the presented feedback method is capable of quantifying the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to three times higher than nearby persons, because of the additional bone-transmitted vibrations.

Acoustics↗
PubMed2003

Anticoagulant therapy in pregnant women with mechanical heart valves.

Managing women with mechanical heart valves during pregnancy poses a particular challenge as there are no available controlled clinical trials to provide guidelines for effective antithrombotic therapy. Oral anticoagulation with coumadin-derivates administration is associated with coumarin embryopathy, and subcutaneous administration of unfractioned heparins (UFH) has been reported to be ineffective in preventing thromboembolic complications. Due to the increased risk of thromboembolic events when UFH is used, low molecular weight heparins (LMWH) were considered to be an alternative. The evidence in the literature regarding the long-term use of LMWH as the only anticoagulant after mechanical heart valve replacement is limited only to a few reports encompassing only 25 patients, with treatment failure in 20%. These data show that anticoagulation with LMWH only is neither safe nor effective in preventing thromboembolic events after mechanical heart valve replacement, in pregnant or non-pregnant women.

Anticoagulants↗
PubMed2005

Comparison of the efficacy and safety profiles of intravenous vitamin K and fresh frozen plasma as treatment of warfarin-related over-anticoagulation in patients with mechanical heart valves.

Patients on warfarin for mechanical heart valves are at increased risk for thromboembolic events and intracranial hemmorhage. In current guidelines, a low dose of vitamin K is the recommended treatment for moderate over-anticoagulation based on studies in which only minority patients participating had mechanical heart valves. We performed a randomized controlled trial to compare the efficacy and safety profile of low-dose intravenous vitamin K and fresh frozen plasma (FFP) for patients with mechanical heart valves and mild to moderate over-anticoagulation (international normalized ratio [INR] 4 to 7). In a 24-month period, we randomized 102 patients to (1) vitamin K or (2) FFP. The baseline INR at presentation between the vitamin K group and the FFP group was 4.61 +/- 0.007 vs 4.78 +/- 0.07 (p = 0.11). Six hours after treatment, patients in the FFP group had a significantly lower mean INR compared with the vitamin K group (2.75 +/- 0.06 vs 3.44 +/- 0.10, p = 0.01). No patient in both groups had over-correction (INR < 2). One week later, there was no significant difference in mean INR between both groups (2.7 +/- 0.11 vs 2.56 +/- 0.12, p = 0.41). Fifty-eight percent of patients in the FFP group and 51% in the vitamin K group had an INR within the target range. There were no adverse reactions or outcomes in both groups. In conclusion, intravenous low-dose vitamin K is a safe alternative to FFP infusion for warfarin overdose in patients with mechanical heart valves.

Anticoagulants↗
PubMedDate not supplied

Observation of cavitation in a mechanical heart valve in a total artificial heart.

Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. The cause of cavitation in mechanical heart valves was investigated using the 25 mm Medtronic Hall valve and the 23 mm Omnicarbon valve. Closing of these valves in the mitral position was simulated in an electrohydraulic totally artificial heart. Tests were conducted under physiologic pressures at heart rates from 60 to 100 beats per minute with cardiac outputs from 4.8 to 7.7 L/min. The disk closing motion was measured by a laser displacement sensor. A high-speed video camera was used to observe the cavitation bubbles in the mechanical heart valves. The maximum closing velocity of the Omnicarbon valve was faster than that of the Medtronic Hall valve. In both valves, the closing velocity of the leaflet, used as the cavitation threshold, was approximately 1.3-1.5 m/s. In the case of the Medtronic Hall valve, cavitation bubbles were generated by the squeeze flow and by the effects of the venturi and the water hammer. With the Omnicarbon valve, the cavitation bubbles were generated by the squeeze flow and the water hammer. The mechanism leading to the development of cavitation bubbles depended on the valve closing velocity and the valve stop geometry. Most of the cavitation bubbles were observed around the valve stop and were generated by the squeeze flow.

Biomechanical Phenomena↗
PubMed2000

Low molecular weight heparin after mechanical heart valve replacement.

BACKGROUND: Patients with mechanical heart valves require life-long anticoagulation. We report here the first large and comparative series of consecutive patients anticoagulated with low molecular weight heparin (LMWH) after mechanical heart valve replacement. METHODS AND RESULTS: In this comparative, nonrandomized study, 208 consecutive patients who underwent a single or double heart valve replacement with mechanical prostheses were anticoagulated subcutaneously with unfractionated heparin (UH) in the first period (n=106) and LMWH in the second phase (n=102) of the study. Baseline characteristics were similar in the 2 groups. The mean durations of UH and LMWH treatments were 13.6+/-0.5 and 14.1+/-0.6 days, respectively (not significant). On the second day of treatment, 87% of patients treated with LMWH had an anti-Xa activity within the range of efficacy (0.5 to 1 IU/mL), but only 9% of UH-treated patients had an activated partial-thromboplastin time value within the therapeutic range (1.5 to 2.5 times control, P<0.0001 between the 2 groups). On the last day of prescription, all LMWH-treated patients had anti-Xa activity above 0.5 IU/mL, but 19% were above 1 IU/mL. In the UH group, 27% of patients had an activated partial-thromboplastin time above 1.5 times control, but 62% were overanticoagulated. Two major bleedings occurred in each group, and one stroke occurred in the UH group. CONCLUSIONS: In this first comparative study, anticoagulation with LMWHs after mechanical heart valve replacement appears feasible, provides adequate biological anticoagulation, and compares favorably with UH anticoagulation. Randomized studies are now needed to further evaluate this new therapeutic approach.

Anticoagulants↗
PubMed1989

Perception of mechanical heart valve sounds.

Most currently used mechanical heart valve prostheses generate a distinct sound when they close. This sound is sometimes disturbing to the patient, and may impair quality of life. In a study of 285 patients followed up for a mean of 2.5 years after mechanical heart valve replacement, one-third were sometimes disturbed by sounds emanating from the prosthesis. Older patients were less disturbed than young ones, but whether this could be explained by age-related impairment of hearing ability (presbyacusis) was not possible to determine. Prosthetic size, implantation site, patient's weight, body surface area and type of prosthesis did not statistically differ according to experience of prosthetic sounds. Although few patients were seriously disturbed by these sounds, it is hoped that mechanical heart valves of the future will function more quietly.

Age Factors↗
PubMed2000

[Circulatory support with the mechanical heart, "HeartMate"].

Treatment with the mechanical heart, HeartMate, has been introduced in Denmark. Short-term circulatory support can be obtained by intraaortic balloon counterpulsation, an external centrifugal pump and the total artificial heart. Long-term circulatory support can be established by treatment with the HeartMate. The principle of the mechanical heart is simple--a pump is implanted in parallel to the existing heart and connected to external, portable batteries. The patient quickly improves and is brought in an optimal state for transplantation. A few patients have been able to omit the subsequent heart transplantation. The patient's own heart improved during the treatment and the native heart functioned again after the system was explanted. The main complications during treatment are bleeding, infection, thromboembolic events and systemic failure. Permanent, fully implantable mechanical circulatory pumps are under development--which may herald the beginning of a whole new era for treatment of cardiac failure.

Assisted Circulation↗
PubMedDate not supplied

DeBakey Surgitool mechanical heart valve prosthesis, explanted at 32 years.

Contemporary mechanical heart value prostheses are expected to last "just about forever" or the patient's lifeline. They do however still suffer complications, some of which necessitate premature explantation. Complications today are mainly related to patient compliance with anticoagulant medication, infection and hemorrhage. The DeBakey Surgitool mechanical heart valve was the first such device to have Pyrolyte components. We present a DeBakey surgitool mechanical heart valve that was in place for 32 years! It was explanted for dysfunction related to tissue overgrowth and not to its related components. With good patient compliance, this mechanical heart valve prosthesis is an example of good prosthetic valve durability.

Aortic Valve↗