Prosthetic Heart Valve Patients Research Articles

Systemic sclerosis and acute heart failure in prosthetic heart valve patients: A retrospective analysis

Systemic sclerosis and acute heart failure in prosthetic heart valve patients: A retrospective analysis

54759 Atopic Dermatitis increases risk of infective endocarditis in prosthetic heart valve patients - A retrospective study

54759 Atopic Dermatitis increases risk of infective endocarditis in prosthetic heart valve patients - A retrospective study

Uncut Gemella Haemolysans: A Case of Bacteremia with No Clear Entry Site

Background: Gemella haemolysans is a gram-positive coccus that colonizes the genitourinary system, gastrointestinal system, and upper respiratory tract as an opportunistic pathogen. Berge et al. found that the frequency of Gemella species bacteremia was 4.5 and infective endocarditis was 0.31 per 1,000,000 inhabitants yearly. We report the first case of G. haemolysans bacteremia presenting as new-onset atrial fibrillation with rapid ventricular response (RVR) and acute respiratory failure and present a case series on G. haemolysans bacteremia and infective endocarditis. Case Presentation: A 58-year-old male with a past medical history including aortic valve bioprosthetic replacement, type 2 diabetes, hypertension, and coronary artery stenting and bypass surgery presented with shortness of breath and confusion. Examination and testing revealed a 40.4°C fever, acute respiratory failure, atrial fibrillation with RVR, congestive heart failure, lactic acidosis, and acute renal failure, with no drug use, dental wounds, or pneumonia. Diltiazem, metoprolol, aspirin, atorvastatin, insulin, heparin, and ceftriaxone were started. TTE and TEE revealed no clear vegetations. Blood cultures revealed Gemella haemolysans. He became stable after 4 days, was electrically cardioverted to sinus rhythm with first-degree AV block, progressed to complete heart block, then had a temporary pacer placed. A repeat TEE demonstrated an aortic root abscess. He underwent redo sternotomy and homograft placement with no complications and was discharged with instructions to complete a six-week course of ceftriaxone. Discussion: Our patient presented with multiple comorbidities at a younger age compared to the mean (66) and median (70) age of the 4 bacteremia cases in our 8-case series. Preemptive antibiotic treatment may be warranted for prosthetic heart valve patients, with the possibility of urgent valve replacement surgery. Several antibiotics were previously reported in case studies with varying results. The shortest course was 16 days, with most courses lasting 4 to 7 weeks. With no standard treatment, this case series suggests G. haemolysans tends to be susceptible to beta-lactam agents. Conclusion: Our case highlights the importance of a multidisciplinary approach in the diagnosis and management of Gemella haemolysans bacteremia, particularly in patients with complex medical histories and prosthetic heart valves.

Bleeding and mortality risk in patients implanted with mechanical prosthetic heart valves with and without thrombocytopenia. Insights from the nationwide PLECTRUM registry

Previous studies showed that mechanical prosthetic heart valve (MPHV) patients may develop thrombocytopenia, but its association with clinical outcomes has not been investigated. We enrolled 1,663 patients with available platelet count from the multicenter nationwide retrospective PLECTRUM registry to investigate the association of thrombocytopenia with all-cause mortality and major bleeding (MB) in patients implanted with MPHV. Thrombocytopenia was defined by platelet count <150 × 109/L. Overall, 44.9% of patients were women and the mean age was 56.7 years. At baseline, 184 (11.1%) patients had thrombocytopenia. Patients with thrombocytopenia were more frequently men and elderly. Platelet count showed an age-dependent decline in men but not in women. We found an increased risk of death in patients with age ≥ 65 years, with a low anticoagulation quality, concomitant arterial hypertension, heart failure, a higher INR range, or with thrombocytopenia (OR 1.739, 95%CI 1.048–2.886, p = .032). At multivariable logistic regression, patients with age ≥65 years, concomitant AF and thrombocytopenia (OR 1.907, 95%CI 1.219–2.983, p = .005) had an increased risk of MBs. In MPHV patients, thrombocytopenia is associated with an increased risk of death and MB. There is a growing need for a sex- and age-specific threshold to define platelet count in adult patients.

Abstract 11885: An App That Brings Guidelines to the Point-of-Care: A Pathway for Anticoagulation in Prosthetic Heart Valves

Introduction: AHA/ACC guidelines are updated regularly, but their clinical implementation at bedside or in the clinic is cumbersome, complicated, and difficult. Apps may fill this gap by bringing medical guidelines to the physician at the bedside. We built the AHA/ACC guidelines as an interactive app that makes the guidelines accessible at the point-of care. This app, in turn, saves time, increases efficiency, and improves the quality of care. Method: While reviewing the AHA/ACC guidelines, we realized that several unique flowcharts can be created each with endpoints being the recommendation for a specific patient characteristic. We used Google App Script and build a spreadsheet-based branching-tree questionnaire with data entry points (e.g., segmented buttons, text data field, or multiple-item selectors) for data inputs. Our data inputs were based on the most recent AHA/ACC guidelines. A unique trigger was set to each data entry item, allowing branching of questions and the users being exposed to a specific subset of questions at each selection. On completion of the clinical module, the app script packages the contents into multiple CSV files (dashboard, pages, contents of each page, and references), and sends the files to Google Firebase, which is Google’s real-time database. In the end, the final recommendation presented is the specific section of the AHA/ACC guideline pertaining to the characteristics of the patient as entered by the user. Qualitative feedback found our app to be “more usable” than the traditional review of guidelines on the website or a paper printout. A subset of the questions for “anticoagulation in prosthetic heart valve patients” is shown in Figure 1. This example represents one of the many modules designed on the same principle. Conclusion: Our interactive app based on AHA/ACC guideline can both save time and improve the quality of care. The app is called “AvoMD”, and we made it available for free on app stores to help clinicians in their practice.

Awareness of medical emergencies among dental practitioners in three Egyptian Dental Schools: A cross-sectional study

Objectives: To evaluate the awareness of medical emergencies among dental practitioners in three dental schools. Material and methods: The study group included 384 dental practitioners, including dental staff members, post-graduate students, and dental interns. These professionals were attending three dental educational institutions in Egypt. Two of them were governmental and one was a private school. The educational model is almost the same in most Egyptian dental schools. Results: The response rate was 100%. Most of the participants worked in private academia (44.16%) or practice (42.34%) and 65.20% of them were females. The participants recorded medical history and filled a form (91.17%, 80.52 % respectively) while only 41.82% obtained the vital signs. Among the participants, 48.57 % were confident about handling medical emergency and 74.29 % reported their capability of intramuscular injection while only 25.71 % for intravenous injection and 49.35% knew about emergency kits. Management knowledge of airway obstruction and prosthetic heart valve patients was reported by 80.27 % and 71.94 % respectively, while less percentage for activation of EMS, chest compression, CPR ratio, and infant rescue breathing. The mean preparedness percent score was 54.57% and it was inversely correlated to the years of experiences and directly correlated to the degree of confidence in their ability to manage the dental emergency. Conclusion: The current study results reflected a deficiency in the dental practitioner awareness about the medical emergency especially the practical part. Keywords Dentists; Cross-sectional studies; Emergencies; Educational models; Dental schools.

Increased intracellular calcium and decreased deformability of erythrocytes from prosthetic heart valve patients

Increased intracellular calcium and decreased deformability of erythrocytes from prosthetic heart valve patients

Multidetector-row computed tomography for prosthetic heart valve dysfunction: is concomitant non-invasive coronary angiography possible before redo-surgery?

Retrospective ECG-gated multidetector-row computed tomography (MDCT) is increasingly used for the assessment of prosthetic heart valve (PHV) dysfunction, but is also hampered by PHV-related artefacts/cardiac arrhythmias. Furthermore, it is performed without nitroglycerine or heart rate correction. The purpose was to determine whether MDCT performed before potential redo-PHV surgery is feasible for concomitant coronary artery stenosis assessment and can replace invasive coronary angiography (CAG). PHV patients with CAG and MDCT were identified. Based on medical history, two groups were created: (I) patients with no known coronary artery disease (CAD), (II) patients with known CAD. All images were scored for the presence of significant (>50 %) stenosis. CAG was the reference test. Fifty-one patients were included. In group I (n = 38), MDCT accurately ruled out significant stenosis in 19/38 (50 %) patients, but could not replace CAG in the remaining 19/38 (50 %) patients due to non-diagnostic image quality (n = 16) or significant stenosis (n = 3) detection. In group II (n = 13), MDCT correctly found no patients without significant stenosis, requiring CAG imaging in all. MDCT assessed patency in 16/19 (84 %) grafts and detected a hostile anatomy in two. MDCT performed for PHV dysfunction assessment can replace CAG (100 % accurate) in approximately half of patients without previously known CAD. • Retrospective MDCT is increasingly used for prosthetic heart valve dysfunction assessment • In case of PHV reoperation, invasive coronary angiography is also required • MDCT can replace CAG in 50 % of patients without coronary artery disease • When conclusive for coronary assessment, MDCT stenosis rule out is highly accurate • Replacing CAG saves associated risks of distant embolization of thrombi or vegetations.

PROSTHESIS-PATIENT MISMATCH IN VALVULAR HEART DISEASE: AN EVALUATION OF ECHOCARDIOGRAPHIC FINDINGS

Guidelines for reporting echocardiographic studies in prosthetic heart valve patients have recently been published. Prothesis-patient mismatch (PPM) was first described in 1978 and is present when the effective orifice area (EOA) of an implanted surgical prosthetic valve is too small in relation to a patient’s body surface area (BSA). PPM remains a common occurrence and has been reported in the literature in up to 20-70% of AVR patients. This is concerning, since undersized prostheses relative to body size may result in higher transprosthetic gradients, worse hemodynamic function and adverse patient outcomes. We examined reporting trends in patients with prosthetic aortic and mitral valves at London Health Sciences Centre (LHSC)and St Joseph's Health Care, with particular focus on PPM in these patient populations. Patients with prosthetic aortic valve replacement (AVR) and/or mitral valve replacement (MVR) undergoing echocardiography between September 2003 and August 2013 were identified. Studies with complete patient data for whom PPM could be measured were included for further analysis. PPM was defined as EOA/BSA ≤ 0.85 cm2/m2 in the aortic position (0.65-0.85 cm2/m2 moderate, <0.65 cm2/m2 severe), and as ≤ 1.3 cm2/m2 in the mitral position. Demographic and echocardiographic parameters were evaluated. Overall 8901 studies from 3378 patients were identified (61% male; mean age 68 ± 13 years). Echocardiographic studies (mean 2.6 studies/patient) were performed in patients with AVR (6290, 71%), MVR (1904, 21%) or both (707, 8%). Complete data sets were obtained for 2391 AVR studies. PPM was present in 44% of AVR studies (severe in 3%). AVR patients with PPM were older at the time of valve replacement (71 vs. 63 years) and at follow-up (73 vs. 65 years), had greater body weight (86 vs. 81kg), larger BSA (1.97 vs. 1.92kg/m2), smaller left ventricular dimensions (47 vs. 49mm), LVOT (19 vs. 20mm) and aortic roots (30 vs. 32mm), with higher transprosthetic gradients (34 vs. 26mmHg) and lower Doppler velocity index (0.41 vs. 0.44) in comparison to patients without PPM (p<0.001 for all). PPM was more common in females (48% vs. 41%, p=0.002), in those with bioprosthetic AVR (56% vs. 9%, p<0.001), with concurrent CABG (52% vs. 39%, p<0.001) and without concurrent aortic root enlargement surgery (46% vs. 32%, p<0.001). The presence of PPM in AVR patients in our study population was common. Our data analysis identified patient subsets with a higher prevalence of PPM, which co-localized with indices of impaired cardiac performance.

Outcomes and total costs of outpatient vs. inpatient peri-procedural anticoagulation management of mechanical prosthetic heart valve patients

Background/objectivesThe most cost-effective periprocedural management of patients with mechanical heart valves (MHV) is uncertain. The objective was to compare the effectiveness, safety and costs for inpatient intravenous unfractionated heparin (IVUH) vs. outpatient low molecular weight heparin (LMWH) “bridging” as periprocedural anticoagulation management for MHV patients. MethodsIn a case-cohort study, Olmsted County, MN residents with MHV who received outpatient periprocedural LMWH management (cases) over the 11-year period, 1997–2007, were matched to residents with MHV who received inpatient IVUH periprocedural management on valve location and type, and on procedure type. Patients were followed for 3months following hospitalization to identify thromboembolism (TE) and major bleeding. Total costs from 30days before to 90days after the procedure were determined from the Olmsted County Healthcare Expenditure and Utilization Database. Outcomes were compared using survival analysis and costs were compared using the Wilcoxon rank sum. Results149 cases (100 aortic, 29 mitral, 20 both; 64% bileaflet) were compared to 149 cohort members (100 aortic, 29 mitral, 20 both; 75% bileaflet). While the 3-month cumulative incidence of TE did not differ significantly among cases (2.7%) and cohort members (4.7%; p=0.36), major bleeding was significantly lower in cases (5.4% vs. 15.4%; p<0.005). Total costs were significantly higher for cohort members ($50,984 vs. $39,347; p=0.002) due to higher inpatient costs ($47,729 vs. $34,860; p=0.0002). ConclusionsOutpatient bridging LMWH therapy is equally effective, but safer and less costly than inpatient IVUH as periprocedural anticoagulation management for MHV patients.

Safety of withholding anticoagulation in patients with mechanical prosthetic valves and intracranial haemorrhage

Patients with prosthetic heart valves require lifelong anticoagulation to prevent thromboembolism. When they have intracranial haemorrhage, anticoagulation has to be withheld. This study was aimed to identify safety duration and complications of anticoagulation withholding in patients with prosthetic heart valves and intracranial haemorrhage. This was a retrospective descriptive study in 26 prosthetic heart valve patients hospitalised in Srinagarind Hospital, Khon Kaen University because of intracranial haemorrhage from 2003 to 2008. Range of anticoagulation withholding was 1 to 26 days with mean 8.5 ± 7.7 days. Most patients (84.6%) were withheld anticoagulation for less than 14 days. There were five in-hospital deaths mostly within 3 days of admission from severe intracranial haemorrhage. No data of reintroduction of anticoagulation was found in three patients because they were lost to follow up. One patient had right basal ganglia infarction after 7 days of anticoagulation withholding. Prosthetic heart valve dysfunction was suspected in one patient who withheld anticoagulant for 76 days. Discontinuation of anticoagulation in patients with prosthetic heart valves and intracranial haemorrhage for less than 7 days was associated with low thromboembolic risk and there was no clinical evidence of prosthetic heart valve dysfunction when anticoagulation was withheld for less than 14 days.

Peri-procedural anticoagulation management of mechanical prosthetic heart valve patients

Introduction To estimate the three-month cumulative incidence of thromboembolism and bleeding among mechanical heart valve (MHV) patients receiving peri-procedural anticoagulation management, consecutive MHV patients referred to the Mayo Clinic Thrombophilia Center for peri-procedural anticoagulation management over the seven-year period, 1997-2003, were followed for three months for thromboembolism, bleeding and vital status. Materials and Methods Warfarin was stopped 4-5 days prior to the procedure, and re-started after the procedure as soon as hemostasis was assured. The decision to provide bridging therapy with low molecular weight (LMWH) or unfractionated (UFH) heparin was individualized and based on the estimated risks of TE and bleeding. Results 556 MHV patients (372 aortic only, 136 mitral only, 48 with multiple valves) underwent 580 procedures. The three-month cumulative incidence of thromboembolism was 0.9% which included: cerebral ischemia (n = 3), unstable angina (n = 1), acute myocardial infarction (n = 1). None were fatal. The cumulative incidence of major bleeding was 3.6% and fatal in 0.2%. The incidence of major bleeding events did not differ by postoperative anticoagulant strategy whether LMWH (3.7%), UFH (6.1%), or no heparin (2.4%) was used (p = 0.26). Conclusions The three-month cumulative incidence of thromboembolism among MHV patients in whom anticoagulation is temporarily interrupted for an invasive procedure is low. Whereas bleeding exceeds thromboembolic complications, our current practice is to restart warfarin as soon as possible post-procedure. Post-procedural heparin use is reserved for patients with the highest thromboembolic risk (mitral MHV, multiple MHVs, MHV with prior stroke or atrial fibrillation) waiting at least 48 hours before initiating.

“Bridging” and Mechanical Heart Valves

Mechanical heart valves require anticoagulation to prevent valve-associated thrombosis and thromboembolic stroke. Oral vitamin K antagonists such as warfarin are prescribed universally; however, oral agents do not act immediately and usually require at least 5 days to achieve a therapeutic effect. Article p 564 Measurement of the prothrombin time, which is standardized by reporting the result as the international normalized ratio (INR), assesses the anticoagulant effect of warfarin. For most mechanical heart valves, the target INR ranges between 2.0 and 3.5. In the postoperative cardiac surgical setting, patients are usually started on low doses of warfarin because they tend to have impaired hepatic metabolism and suboptimal nutritional status. Even with low initial doses of warfarin, mechanical heart valve replacement patients are susceptible to excessively high INRs.1 This known exaggerated initial response to warfarin after heart valve replacement can lead to the habitual prescription of such low warfarin doses that warfarin as monotherapy may not achieve a stable and therapeutic INR for weeks after its initiation. To minimize the delay in achieving therapeutic anticoagulation, a “bridging” anticoagulant is prescribed. The “bridge” is administered parenterally, thereby providing an immediate anticoagulant effect. Traditionally, the “bridging” agent has been unfractionated heparin (UFH). More recently, physicians tend to select low-molecular-weight heparin (LMWH), even though few studies exist to validate the efficacy and safety of either LMWH or UFH in this setting. The rationale for shunning UFH has been to avoid the known perils and inconveniences of its use as a continuous peripheral intravenous infusion. UFH is rarely administered in an immediately therapeutic dose because of fear of precipitating bleeding complications. Especially in postoperative mechanical valve replacement patients, there is reluctance to follow the high dosing requirements for initial bolus and infusion regimens published in standardized nomograms. Instead, UFH is usually started in cautious small …

Resolved: Heparin may be useful in selected patients with brain ischemia.

Heparin reduces development of erythrocyte-fibrin thrombi that form in regions of vascular stasis especially within the heart, in severely stenosed arteries sometimes engrafted on white thrombi, in acute arterial occlusions as fresh tails on existing thrombi, and within extremity and pelvic veins. Unfortunately, heparin use can be associated with severe bleeding, especially if not closely monitored. Heparin should not be indiscriminately used in all brain ischemia patients. Bleeding complications will outweigh therapeutic benefit. Unfortunately, randomized trials have not adequately studied heparins in patients with conditions likely to respond to treatment. Reported trials lumped patients with brain ischemia together without diagnostic investigations defining etiology, stroke subtypes, or vascular lesions. Worsening and new neurologic deficits can develop when thrombi form, propagate, and embolize. Stroke worsening, even when thrombi are present, occurs in only 20% to 33% of ischemic strokes. Even when anticoagulants are stopped because of hemorrhage in prosthetic heart valve patients, recurrent embolism rarely occurred during the next 10 days.1 Most cardioembolic recurrences do not occur during …

How Safely and for How Long Can Warfarin Therapy Be Withheld in Prosthetic Heart Valve Patients Hospitalized With a Major Hemorrhage?

To identify the risk of thromboembolism after withholding or reversing the effect of warfarin therapy following a major hemorrhage. Retrospective medical record review. Tertiary-care hospital. Twenty-eight patients with prosthetic heart valves receiving warfarin were hospitalized for major hemorrhage from 1990 to 1997. The mean +/- SD age was 61 +/- 11 years (15 men and 13 women). Twenty patients had St. Jude valves, 4 patients had Carpentier-Edwards bioprosthetic valves, 2 patients had Starr Edwards valves, and 2 patients had Bjork-Shiley valves. Valves were in the mitral position in 12 patients, the aortic position in 12 patients, and both mitral and aortic positions in 4 patients. The average interval from valve surgery to index bleeding was 7 years. Twenty-five patients had GI or retroperitoneal hemorrhage, 2 patients had an intracranial hemorrhage, and 1 patient had a subdural hematoma. Vitamin K was administered to five patients and fresh frozen plasma was given to seven patients to reverse anticoagulation. The mean duration of anticoagulation withholding was 15 +/- 4 days. None of the patients had thromboembolic complications. There were four in-hospital deaths. Twenty-two of the 24 hospital survivors resumed warfarin therapy at hospital discharge. At 6-month follow-up, 10 of 19 patients remaining on warfarin therapy had recurrent GI bleeding. Thromboembolic risk is low in prosthetic heart valve patients hospitalized with major hemorrhage when their warfarin therapy is reversed or withheld. Recurrent bleeding within 6 months of the resumption of anticoagulation is common, and aggressive treatment of the bleeding source and the risk-benefit ratio of continued anticoagulation need to be considered.

MULTIFREQUENCY DOPPLER DISCRIMINATES BETWEEN GASEOUS AND SOLID MICROEMBOLI

110 Introduction: Although cerebral microemboli may be detected using transcranial Doppler, it is at present extremely difficult to determine if they are composed of gaseous or solid elements. Theoretically this is possible by insonating an embolus simultaneously with two different ultrasound frequencies since the reflected ultrasound power will differ for each frequency depending on embolus type. Methods: The Doppler instrumentation used in this study discriminates between solid and gaseous microemboli by insonating them simultaneously with 2.0 and 2.5 MHz frequencies. In the experimental part of the study 61 solid (50–80 μm plastic) and 45 gaseous (15–30 μm) microemboli were introduced into a pulsatile closed-loop system. Five prosthetic heart valve patients and 10 carotid artery stenosis patients took part in the clinical studies. Results : In the experimental study analysis of the reflected Doppler power for the two different ultrasound frequencies showed correct differentiation between solid (N = 61) and gaseous (N = 45) microemboli for 95% of the microembolic events. Four hundred microemboli in the 5 prosthetic heart valve patients and 20 microemboli in the 10 carotid stenosis patients were analysed. In the prosthetic heart valve patients 344 (86%) were gaseous and 56 (14%) solid whereas all 20 (100%) microemboli in the carotid stenosis patients were solid. Conclusions: These studies have shown that it is now possible to discriminate between solid and gaseous cerebral microemboli using multifrequency transcranial Doppler monitoring.

MULTIFREQUENCY DOPPLER DISCRIMINATES BETWEEN GASEOUS AND SOLID MICROEMBOLI

110 Introduction: Although cerebral microemboli may be detected using transcranial Doppler, it is at present extremely difficult to determine if they are composed of gaseous or solid elements. Theoretically this is possible by insonating an embolus simultaneously with two different ultrasound frequencies since the reflected ultrasound power will differ for each frequency depending on embolus type. Methods: The Doppler instrumentation used in this study discriminates between solid and gaseous microemboli by insonating them simultaneously with 2.0 and 2.5 MHz frequencies. In the experimental part of the study 61 solid (50–80 μm plastic) and 45 gaseous (15–30 μm) microemboli were introduced into a pulsatile closed-loop system. Five prosthetic heart valve patients and 10 carotid artery stenosis patients took part in the clinical studies. Results : In the experimental study analysis of the reflected Doppler power for the two different ultrasound frequencies showed correct differentiation between solid (N = 61) and gaseous (N = 45) microemboli for 95% of the microembolic events. Four hundred microemboli in the 5 prosthetic heart valve patients and 20 microemboli in the 10 carotid stenosis patients were analysed. In the prosthetic heart valve patients 344 (86%) were gaseous and 56 (14%) solid whereas all 20 (100%) microemboli in the carotid stenosis patients were solid. Conclusions: These studies have shown that it is now possible to discriminate between solid and gaseous cerebral microemboli using multifrequency transcranial Doppler monitoring.

Restarting anticoagulation in prosthetic heart valve patients after intracranial haemorrhage: a 2-year follow-up.

35 patients with oral anticoagulant (OAC) related intracranial or intraspinal haemorrhage were studied to determine treatment received, outcome and rate of recurrent bleeding and thromboembolism after restarting OAC. All patients underwent active anticoagulant reversal and in 14 patients with prosthetic heart valves (PHV) the INR remained below 2.0 for 0-19d (median 7) with no thromboembolic events. 10 patients received heparin, although a therapeutic level was rarely achieved. 13 patients with PHV were restarted on OAC and followed for a median 23.5 months. One patient had recurrent intracranial bleeding. 3/13 patients had cerebral embolic events despite anticoagulation. We conclude that in PHV patients temporary cessation of OAC is safe and the risk of recurrent bleeding after restarting OAC is low.

Transcranial Doppler detection of microemboli in prosthetic heart valve patients: dependency upon valve type

Transcranial Doppler ultrasound has revealed the existence of cerebrovascular microemboli in asymptomatic patients with prosthetic heart valves. We investigated the relation between the presence and number of emboli signals and valve type. Patients with six types of prosthetic valves (Björk-Shiley monostrut, Medtronic-Hall, Carbomedics, ATS, Carpentier-Edwards standard, Carpentier-Edwards supraannular) were examined using transcranial Doppler ultrasound in two centers. The monitoring time was 30 min over the right middle cerebral artery. All patients were stabilized on warfarin at the time of study. Microemboli signals were identified by their characteristic audiovisual signal and on subsequent spectral analysis, based on accepted criteria. A standard neurologic questionnaire was completed by all patients. The prevalence of microemboli signals varied between 49% (Medtronic Hall) and 97% (Björk-Shiley monostrut), while their number varied between 1 [0-3] (Carpentier-Edwards standard) and 187 [136-240] (Björk-Shiley monostrut) per hour (median and 95% CI). Both parameters were significantly higher in patients with Björk-Shiley monostrut valves compared to the other patient groups. There were no significant differences in the prevalence of neurologic complications among the groups examined (overall 16%), or in emboli numbers between symptomatic and asymptomatic patients. The prevalence and quantity of microemboli signals in patients with prosthetic heart valves, as detected by transcranial Doppler, is dependent upon valve type. The clinical significance of these microemboli signals remains to be further evaluated.

On the origin of cerebrovascular microemboli associated with prosthetic heart valves

Application of transcranial Doppler ultrasonography to asymptomatic prosthetic heart valve patients can result in the detection of transient high intensity signals, similar to those induced by the passage of emboli. However, the origin of these signals is unknown. An in vitro study has been undertaken to investigate the capacity of prosthetic heart valves to generate high intensity Doppler signals in the absence of blood. A pulse duplicator, filled with a seeded saline solution, was used to function prosthetic heart valves under mock-physiological conditions. A Björk-Shiley Monostrut valve was mounted in the aortic port while a tri-leaflet control valve was fixed in the mitral port. At stations upstream and downstream from the Björk-Shiley valve, flow was monitored using pulsed wave Doppler ultrasound (Nicolet TC-2000, 2 MHz probe). The effect of damping the harsh closure of the mechanical valve was investigated by applying a thin layer of soft adhesive tape between the valve occluder and outer ring. For all valve configurations, transient high intensity Doppler signals, characteristic of microemboli and similar to those observed in clinical studies of prosthetic heart valve patients, were detected downstream from the aortic port. The number of microemboli signals did not change significantly between sites at 20 cm and 40 cm downstream from the aortic valve. Damping the Björk-Shiley valve closure greatly reduced (by 80%) the number of microemboli signals detected. It is concluded that Doppler microemboli signals can be generated by prosthetic heart valves while functioning in the absence of the formed elements of blood, and that the number of microemboli signals produced depends upon the rate of energy dissipation at valve closure.