Cineradiography for determination of normal and abnormal function in mechanical heart valves

Leaflet Fracture and Embolization of a CarboMedics Prosthetic Mitral Valve

Fracture of prosthetic valve leaflets in the absence of traumatic injury is very rare. Leaflet fracture can cause acute pulmonary edema and cardiogenic shock and is potentially life-threatening, requiring emergency surgery. Thus, a leaflet fracture must be diagnosed quickly and accurately. We present the case of a 46-year-old man with CarboMedics prosthetic aortic and mitral valve replacements implanted 24 years previously. The patient presented at our emergency department with abrupt dyspnea and fever. We diagnosed severe mitral valve regurgitation with anterior leaflet fracture. The patient underwent venoarterial extracorporeal membrane oxygenation and delayed mitral valve replacement. The foreign body was removed step by step because the diagnosis was missed. Two pieces of broken leaflets were found in the left common iliac artery and left external iliac artery. The patient was treated successfully and remains asymptomatic 1 year following surgery.

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

This executive summary of the valvular heart disease guideline provides recommendations for clinicians to diagnose and manage valvular heart disease as well as supporting documentation to encourage their use.

METHODS

A comprehensive literature search was conducted from January 1, 2010, to March 1, 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, Cochrane, Agency for Healthcare Research and Quality Reports, and other selected database relevant to this guideline. Structure: Many recommendations from the earlier valvular heart disease guidelines have been updated with new evidence and provides newer options for diagnosis and treatment of valvular heart disease. This summary includes only the recommendations from the full guideline which focus on diagnostic work-up, the timing and choice of surgical and catheter interventions, and recommendations for medical therapy. The reader is referred to the full guideline for graphical flow charts, text, and tables with additional details about the rationale for and implementation of each recommendation, and the evidence tables detailing the data considered in developing these guidelines.

Possible Assessment of Calf Venous Pump Efficiency by Computational Fluid Dynamics Approach

Three-dimensional simulations of peripheral, deep venous flow during muscular exercise in limbs of healthy subjects and in those with venous dysfunction were carried out by a computational fluid-dynamics (CFD) approach using the STAR CCM + platform. The aim was to assess the effects of valvular incompetence on the venous calf pump efficiency. The model idealizes the lower limb circulation by a single artery, a capillary bed represented by a porous region and a single vein. The focus is on a segment of the circuit which mimics a typical deep vein at the level of the calf muscle, such as the right posterior tibial vein. Valves are idealized as ball valves, and periodic muscle contractions are given by imposing time-dependent boundary conditions to the calf segment wall. Flow measurements were performed in two cross-sections downstream and upstream of the calf pump. Model results demonstrate a reduced venous return for incompetent valves during calf exercise. Two different degrees of valvular incompetence are considered, by restricting the motion of one or both valves. Model results showed that only the proximal valve is critical, with a 30% reduction of venous return during calf exercise in case of valvular incompetence: the net flow volume ejected by the calf in central direction was 0.14 mL per working cycle, against 0.2 mL for simulated healthy limbs. This finding appeared to be consistent with a 25% reduction of the calf ejection fraction, experimentally observed in chronic venous disease limbs compared with healthy limbs.

Prosthetic mitral valve leaflet escape

Leaflet escape of prosthetic valve is rare but potentially life threatening. It is essential to make timely diagnosis in order to avoid mortality. Transesophageal echocardiography and cinefluoroscopy is usually diagnostic and the location of the missing leaflet can be identified by computed tomography (CT). Emergent surgical correction is mandatory. We report a case of fractured escape of Edward-Duromedics mitral valve 27 years after the surgery. The patient presented with symptoms of acute decompensated heart failure and cardiogenic shock. She was instantly intubated and mechanically ventilated. After prompt evaluation including transthoracic echocardiography and CT, the escape of the leaflet was confirmed. The patient underwent emergent surgery for replacement of the damaged prosthetic valves immediately. Eleven days after the surgery, the dislodged leaflet in iliac artery was removed safely and the patient recovered well.

Prosthetic mitral valve thrombosis: can fluoroscopy predict the efficacy of thrombolytic treatment?

BACKGROUND

Thrombolysis (T) is an effective therapy for prosthetic valve thrombosis (PVT). Debate still exists as to which clinical or noninvasive finding best predict the result of T. The aim of the study was to investigate the role of fluoroscopy (F) to predict efficacy of T in pts with mitral PVT.

METHODS

We evaluated 17 consecutive pts with bileaflet mitral PVT. F criteria for PVT were: abnormal disc motion and calculated opening angle >25 degrees. T was carried out with tissue-type plasminogen activator (tPA; 100 mg over 3 hours followed by heparin infusion for 24 hours) and was considered successful when normalization of leaflet motion and opening angle occurred. Results were evaluated according to symptom duration (<21 days, early PVT; >21 days, late PVT) and to F pattern of PVT (blocked leaflet versus hypomobile leaflet).

RESULTS

F showed disc motion alteration in 24 of 34 leaflets: 8 leaflets were blocked, whereas 16 were hypomobile. Early (12.7+/-6.1 days, range 3-21) and late (113+/-114 days, range 28-365) PVT was present in 8 and 7 pts, respectively. Thrombolysis was successful in 20 of 24 leaflets. Blocked leaflet fully recovered only in early PVT (n=4) pts, whereas they remained blocked in late PVT (n=4). On the contrary, in all of the cases with hypomobile leaflet, disc motion normalized regardless duration of symptoms and extent of disc motion reduction. Interestingly, 4 leaflets with late PVT was diagnosed as blocked by trans-thoracic (TTE). F showed a residual disc movement in all: they fully recovered after T. Two pts with late PVT had both leaflets affected (1 blocked +1 hypomobile); although blocked leaflet did not respond to T, the normalization of hypomobile significantly improved clinical condition.

CONCLUSIONS

F can predict result of T in mitral PVT. PVT with F evidence of hypomobile leaflet always recovers regardless of symptom duration and extent of disc motion reduction, suggesting that the small amount of thrombus needed to interfere with discs motion in bileaflet prostheses remains sensitive to T even after a long time. PVT with F evidence of blocked leaflet has a favorable response to T only in case of early PVT. Late PVT with blocked leaflet does not respond to T, suggesting a larger and stratified thrombus and the coexistence of pannus and, in our series, always required surgery. However, if a hypomobile leaflet coexists, T may be used to restore normal movement of hypomobile leaflet so that to improve patient clinical and hemodynamic condition before operation.

Cardiopulmonary bypass before general anesthesia in prosthetic valve thrombosis

Valve obstruction is a lifethreatening complication of mechanical valve prostheses. Emergency operation is mandatory for patients who subsequently develop cardiogenic shock and severe pulmonary edema. In this severely compromised hemodynamic condition, cardiac arrest develops in most of the patients before surgery and just after general anesthesia induction. In one such case, we performed femorofemoral cardiopulmonary bypass with local anesthesia before general anesthesia induction and successfully replaced the thrombosed prosthetic valve, thus avoiding a catastrophic outcome.

Role of cine-fluoroscopy, transthoracic, and transesophageal echocardiography in patients with suspected prosthetic heart valve thrombosis

Prosthetic heart valve thrombosis (PVT) is a rare but potentially life-threatening complication of heart valve replacement. An effective, quick, and easy diagnostic method is highly desirable. We evaluated the diagnostic efficacy of cine-fluoroscopy (CF), transthoracic (TTE), and transesophageal (TEE) echocardiography in 82 consecutive patients with mechanical valves and suspected PVT. Criteria for PVT were: leaflet(s) motion restriction at CF, increased Doppler gradients at TTE, and evidence of thrombi at TEE. Patients were divided in 4 groups (A, B, C, and D) according to results of CF and TTE. Group A was composed of 24 patients with positive CF and TTE. Thrombi were detected by TEE in all cases, suggesting that when both are positive, CF and TTE correctly identified PVT in all patients so that TEE may be deferred. Group B was composed of 12 patients with positive CF and negative TTE; TEE showed PVT in 4 patients (33%). These patients had very slight leaflet motion restriction as in the case of initial PVT. This suggests that CF compared with Doppler may identify patients with "hemodynamically significant" PVT. The remaining 8 patients in this group had monocuspid prostheses with negative TEE, suggesting that abnormal leaflet motion at CF may be due to functional changes. Therefore, TEE should always be performed in case of monocuspid prostheses with isolated CF abnormalities. Group C was composed of 18 asymptomatic patients with small-sized aortic prostheses and very high Doppler gradients on routine TTE. CF showed normal leaflet motion and TEE ruled out PVT in all cases outlining the diagnostic role of CF in this particular subset. Finally, group D was composed of 28 patients with negative CF and TTE. TEE did not show thrombi in 24 of 28 patients (86%), confirming that, when both yield negative results, CF and TTE are reliable methods to rule out valve thrombosis in most cases. However, in 4 of 28 patients (14%) TEE showed "nonobstructive" prosthetic thrombosis: these patients had mitral prostheses, chronic atrial fibrillation, and 3 of 4 had systemic embolisms. Thus, TEE should be performed in selected patients despite negative CF and TTE results. Sensitivity, specificity, and positive and negative predictive values were 87%, 78%, 80%, and 91% for CF and 75%, 64%, 57%, and 78% for TTE, respectively. CF and TTE correctly identified PVT in 70 of 82 patients (85%). TEE was actually required in 15% of the cases. Thus, CF and TTE are quick, effective, and complementary diagnostic tools to diagnose PVT in most patients. TEE still remains the gold standard technique in selected cases.

Thrombosis of mechanical heart valve prostheses: revisiting the role of fluoroscopy

Prosthetic valve thrombosis is a rare but potentially fatal complication of heart valve replacement. Symptoms may be misleading, yet the condition may rapidly lead to death. A prompt diagnosis is therefore crucial. Ultrasound is the most often used technique for evaluating prosthesis dysfunction. We describe two cases of prosthesis thrombosis with negative Doppler results but with distinctly abnormal leaflet motion at fluoroscopy. A correct diagnosis would have been missed if the Doppler evaluation alone was relied on. Fluoroscopy should always form part of the diagnostic work-up in patients with artificial heart valves.

Reference Doppler echocardiographic values for St. Jude Medical, Omnicarbon, and Biocor prosthetic valves in the aortic position

The objectives of the present investigation were (1) to describe Doppler echocardiographic findings for mechanical and biologic aortic valves at an early stage after operation and later in a stable phase and (2) to study the changes occurring between these investigations. Patients (n = 213) who received a mechanical (St. Jude Medical, Omnicarbon) or a biologic (Biocor) valve were studied by Doppler echocardiography within the first week (baseline, n = 203) and after 2 years (late, n = 172). The comparison of baseline with late investigation (mean +/- SD) showed an increase in systolic blood pressure (137 +/- 18.5 to 154 +/- 20.6 mm Hg, p = 0.0001, n = 112), reduction of heart rate (85 +/- 15.3 to 74 +/- 12.0 beats/min, p = 0.0001, n = 141) and increase in stroke volume (59 +/- 20.6 to 77 +/- 19.8 ml, p = 0.0001, n = 132). Prosthetic Doppler echocardiographic findings demonstrated a reduction in blood flow velocity in the left ventricular outflow tract (VLVOT, 1.10 +/- 0.25 to 0.96 +/- 0.23 m/sec, p = 0.0001, n = 146) reduction in peak velocity (Vmax 2.72 +/- 0.53 to 2.59 +/- 0.54 m/sec, p = 0.02, n = 150), reduction in mean pressure gradient (deltaPmean, 18.4 +/- 7.2 to 16.3 +/- 7.3 mm Hg, p = 0.004) and an increase in velocity index (Vmax/VLVOT, 2.56 +/- 0.62 to 2.67 +/- 0.60, p = 0.003, n = 144). The standard deviations of difference between baseline and late investigation expressed as percentage of mean were 25% for VLVOT, 20% for Vmax, 44% for deltaPmean, and 25% for velocity index. In conclusion, this large reference base provides data that should be useful for the clinician evaluating patients with prosthetic valves early after valve replacement as well as at a later stage. When valve dysfunction is suspected a previous investigation for comparison is helpful, and our data describe the changes that normally may be seen between an early baseline and a late investigation.

Quantitative assessment of the presence of a single leg separation in Björk-Shiley convexoconcave prosthetic heart valves

RATIONALE AND OBJECTIVES

The authors developed an analytic software package for the objective and reproducible assessment of a single leg separation (SLS) in the outlet strut of Björk-Shiley convexoconcave (BSCC) prosthetic heart valves.

METHODS

The radiographic cinefilm recordings of 18 phantom valves (12 intact and 6 SLS) and of 43 patient valves were acquired. After digitization of regions of interest in a cineframe, several processing steps were carried out to obtain a one-dimensional corrected and averaged density profile along the central axis of each strut leg. To characterize the degree of possible separation, two quantitative measures were introduced: the normalized pit depth (NPD) and the depth-sigma ratio (DSR). The group of 43 patient studies was divided into a learning set (25 patients) and a test set (18 patients).

RESULTS

All phantom valves with an SLS were detected (sensitivity, 100%) at a specificity of 100%. The threshold values for the NPD and the DSR to decide whether a fracture was present or not were 3.6 and 2.5, respectively. On the basis of the visual interpretations of the 25 patient studies (learning set) by an expert panel, it was concluded that none of the patients had an SLS. To achieve a 100% specificity by quantitative analysis, the threshold values for the NPD and the DSR were set at 5.8 and 2.5, respectively, for the patient data. Based on these threshold values, the analysis of patient data from the test set resulted in one false-negative detection and three false-positive detections.

CONCLUSIONS

An analytic software package for the detection of an SLS was developed. Phantom data showed excellent sensitivity (100%) and specificity (100%). Further research and software development is needed to increase the sensitivity and specificity for patient data.

Elective reoperation for a strut fracture in a Björk-Shiley convexo-concave mitral valve

A 71-year-old asymptomatic man who had previously undergone mitral valve replacement with a 31-mm Björk-Shiley 60-degree convexo-concave valve was evaluated noninvasively and found to have a single leg outlet strut separation. Elective valve explantation was performed, and valve testing confirmed that a strut separation was indeed present. Diagnosis and early reoperation to replace a fractured prosthesis may improve patient survival.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.