Calculation of mitral regurgitant orifice area with use of a simplified proximal convergence method: initial clinical application

Quantification of primary mitral regurgitation by echocardiography: A practical appraisal

The accurate quantification of primary mitral regurgitation (MR) and its consequences on cardiac remodeling is of paramount importance to determine the best timing for surgery in these patients. The recommended echocardiographic grading of primary MR severity relies on an integrated multiparametric approach. It is expected that the large number of echocardiographic parameters collected would offer the possibility to check the measured values regarding their congruence in order to conclude reliably on MR severity. However, the use of multiple parameters to grade MR can result in potential discrepancies between one or more of them. Importantly, many factors beyond MR severity impact the values obtained for these parameters including technical settings, anatomic and hemodynamic considerations, patient's characteristics and echocardiographer' skills. Hence, clinicians involved in valvular diseases should be well aware of the respective strengths and pitfalls of each of MR grading methods by echocardiography. Recent literature highlighted the need for a reappraisal of the severity of primary MR from a hemodynamic perspective. The estimation of MR regurgitation fraction by indirect quantitative methods, whenever possible, should be central when grading the severity of these patients. The assessment of the MR effective regurgitant orifice area by the proximal flow convergence method should be used in a semi-quantitative manner. Furthermore, it is crucial to acknowledge specific clinical situations in MR at risk of misevaluation when grading severity such as late-systolic MR, bi-leaflet prolapse with multiple jets or extensive leak, wall-constrained eccentric jet or in older patients with complex MR mechanism. Finally, it is debatable whether the 4-grades classification of MR severity would be still relevant nowadays, since the indication for mitral valve (MV) surgery is discussed in clinical practice for patients with 3+ and 4+ primary MR based on symptoms, specific markers of adverse outcome and MV repair probability. Primary MR grading should be seen as a continuum integrating both quantification of MR and its consequences, even for patients with presumed “moderate” MR.

Impact of assuming a circular orifice on flow error through elliptical regurgitant orifices: computational fluid dynamics and in vitro analysis of proximal flow convergence

Grounded in hydrodynamic theory, proximal isovelocity surface area (PISA) is a simplistic and practical technique widely used to quantify valvular regurgitation flow. PISA provides a relatively reasonable, though slightly underestimated flow rate for circular orifices. However, for elliptical orifices frequently seen in functional mitral regurgitation, PISA underestimates the flow rate. Based on data obtained with computational fluid dynamics (CFD) and in vitro experiments using systematically varied orifice parameters, we hypothesized that flow rate underestimation for elliptical orifices by PISA is predictable and within a clinically acceptable range. We performed 45 CFD simulations with varying orifice areas 0.1, 0.3 and 0.5 cm², orifice aspect ratios 1:1, 2:1, 3:1, 5:1, and 10:1, and peak velocities (V_max) 400, 500 and 600 cm/s. The ratio of computed effective regurgitant orifice area to true effective area (EROA_C/EROA) against the ratio of aliasing velocity to peak velocity (V_A/V_max) was analyzed for orifice shape impact. Validation was conducted with in vitro imaging in round and 3:1 elliptical orifices. Plotting EROA_C/EROA against V_A/V_max revealed marginal flow underestimation with 2:1 and 3:1 elliptical axis ratios against a circular orifice (< 10% for 8% V_A/V_max), rising to ≤ 35% for 10:1 ratio. In vitro modeling confirmed CFD findings; there was a 8.3% elliptical EROA underestimation compared to the circular orifice estimate. PISA quantification for regurgitant flow through elliptical orifices produces predictable, but generally small, underestimation deemed clinically acceptable for most regurgitant orifices.

The influence of chest wall conformation on myocardial strain parameters in a cohort of mitral valve prolapse patients with and without mitral annular disjunction

PURPOSE

To evaluate the possible influence of chest wall conformation on myocardial strain parameters in a cohort of mitral valve prolapse (MVP) patients with and without mitral annular disjunction (MAD).

METHODS

All consecutive middle-aged patients with MVP referred to our Outpatient Cardiology Clinic for performing two-dimensional (2D) transthoracic echocardiography (TTE) as part of work up for primary cardiovascular prevention between March 2018 and May 2022, were included into the study. All patients underwent clinic visit, physical examination, modified Haller index (MHI) assessment (the ratio of chest transverse diameter over the distance between sternum and spine) and conventional 2D-TTE implemented with speckle tracking analysis of left ventricular (LV) global longitudinal strain (GLS) and global circumferential strain (GCS). Independent predictors of MAD presence on 2D-TTE were assessed.

RESULTS

A total of 93 MVP patients (54.2 ± 16.4 yrs, 50.5% females) were prospectively analyzed. On 2D-TTE, 34.4% of MVP patients had MAD (7.3 ± 2.0 mm), whereas 65.6% did not. Compared to patients without MAD, those with MAD had: 1) significantly shorter antero-posterior (A-P) thoracic diameter (13.5 ± 1.2 vs 14.8 ± 1.3 cm, p < 0.001); 2) significantly smaller cardiac chambers dimensions; 3) significantly increased prevalence of classic MVP (84.3 vs 44.3%, p < 0.001); 4) significantly impaired LV-GLS (-17.2 ± 1.4 vs -19.4 ± 3.0%, p < 0.001) and LV-GCS (-16.3 ± 4.1 vs -20.4 ± 4.9, p < 0.001), despite similar LV ejection fraction (63.7 ± 4.2 vs 63.0 ± 3.9%, p = 0.42). A-P thoracic diameter (OR 0.25, 95%CI 0.10-0.82), classic MVP (OR 3.90, 95%CI 1.32-11.5) and mitral annular end-systolic A-P diameter (OR 2.76, 95%CI 1.54-4.92) were the main independent predictors of MAD. An A-P thoracic diameter ≤ 13.5 cm had 59% sensitivity and 84% specificity for predicting MAD presence (AUC = 0.81). In addition, MAD distance was strongly influenced by A-P thoracic diameter (r = - 0.96) and MHI (r = 0.87), but not by L-L thoracic diameter (r = 0.23). Finally, a strong inverse correlation between MHI and both LV-GLS and LV-GCS was demonstrated in MAD patients (r = - 0.94 and - 0.92, respectively), but not in those without (r = - 0.51 and - 0.50, respectively).

CONCLUSIONS

A narrow A-P thoracic diameter is strongly associated with MAD presence and is a major determinant of the impairment in myocardial strain parameters in MAD patients, in both longitudinal and circumferential directions.

Basic Principles of the Echocardiographic Evaluation of Mitral Regurgitation

Mitral regurgitation (MR) is a common form of valvular heart disease that is associated with significant morbidity and mortality. Treatment decisions are completely dependent on accurate diagnosis of both mechanism and severity of MR, which can be challenging and is often done incorrectly. Transthoracic echocardiography is the most commonly used imaging test for MR; transesophageal echocardiography is often needed to better define morphology and MR severity, and is essential for guiding transcatheter therapies for MR. Multidetector computed tomography has become the standard to assess whether transcatheter valve replacement is an option because of its ability to assess valve sizing, access, and potential left ventricular outflow tract obstruction. Finally, cine cardiac magnetic resonance has been recommended by recent guidelines to quantify MR severity when the distinction between moderate and severe MR is indeterminate by echocardiography. This paper focuses on the main questions to be answered by imaging techniques and illustrates some common tips, tricks, and pitfalls in the assessment of MR.

Stiff Left Atrial Syndrome; Prospects and Possibilities. Retrospective Analysis and Review of the Literature

OBJECTIVES

Stiff left atrial syndrome is an intriguing clinical phenomena characterized by reduced left atrial compliance, pulmonary venous hypertension and exacerbations of volume overload. We conducted a retrospective review of patients diagnosed with stiff left atrial syndrome at our center.

METHODS

All patients admitted to our hospital with volume overload and pulmonary venous hypertension who were diagnosed with stiff left atrial syndrome based on evidence by echocardiogram and right heart catheterization between July 2011 and July 2013 were included in this retrospective review.

RESULTS

Twentythree patients (mean age 73 ± 11 years, 39% male and 61% female) were diagnosed with stiff left atrial syndrome at our center. Thirty-five percent had persistent while 39% had permanent atrial fibrillation. Mean duration of atrial fibrillation was 7.6 ± 2.1 years. Forty-three percent of patients had long standing hypertension. There was no mitral regurgitation in 39% of patients while 48% had mild mitral regurgitation. On right heart catheterization, mean right atrial pressure was 12.6±4.8 mm of Hg, mean pulmonary arterial pressure was 33±7.2 mm of Hg, mean pulmonary capillary wedge pressure was 24.8± 4.2mm of Hg while peak V waves were seen at mean of 37.8± 5.3 mm of Hg. Mean left atrial volume index was 49.8±17.1 mL/m 2. After the initial diagnosis with a two year follow- up, there were no readmissions in 65% of patients who were on appropriate diuretic therapy and had regular clinical visits. Frequent readmissions were seen in 35% of patients inspite of appropriate diuretic therapy. All-cause mortality rate was 4.3% at two year follow up.

CONCLUSION

In patients with stiff left atrial syndrome, the presence of left atrial dilation, long standing atrial fibrillation and hypertension are the key factors associated with pathogenesis and clinical course. Close follow up and monitoring of volume status is essential to prevent hospital readmissions and improve long term prognosis.

Multimodality imaging for the quantitative assessment of mitral regurgitation

The natural history of mitral regurgitation (MR) results in significant morbidity and mortality. Innovations in non-invasive imaging have provided new insights into the pathophysiology and quantification of MR, in addition to early detection of left ventricular (LV) dysfunction and prognostic assessment in asymptomatic patients. Transthoracic (TTE) and transesophageal (TOE) echocardiography are the mainstay for diagnosis, assessment and serial surveillance. However, the advance from 2D to 3D imaging leads to improved assessment and characterization of mitral valve (MV) disease. Cardiovascular magnetic resonance (CMR) is increasingly used for MR quantitation and can provide an alternative imaging method if echocardiography is suboptimal or inconclusive. Other techniques such as exercise echocardiography, tissue Doppler imaging and speckle-tracking echocardiography can further offer complementary information on prognosis. This review summarises the current evidence for state-of-the-art cardiovascular imaging for the investigation of MR. Whilst advanced echocardiographic techniques are superior in the evaluation of complex MV anatomy, CMR appears the most accurate technique for the quantification of MR severity. Integration of multimodality imaging for the assessment of MR utilises the advantages of each imaging technique and offers the most comprehensive assessment of MR.

Primary mitral valve regurgitation: Update and review

Mitral regurgitation is the second most common valvular disorder requiring surgical intervention worldwide. This review summarizes the current understanding of primary, degenerative mitral regurgitation with respect to etiology, comprehensive assessment, natural history and management. The new concept of staging of the valvular disorders, newer predictors of adverse and controversy of “watchful waiting” versus “early surgical intervention” for severe, asymptomatic, primary mitral regurgitation are addressed.

Automated quantification of mitral regurgitation by three dimensional real time full volume color Doppler transthoracic echocardiography: a validation with cardiac magnetic resonance imaging and comparison with two dimensional quantitative methods

BACKGROUND

Accurate assessment of mitral regurgitation (MR) severity is crucial for clinical decision-making and optimizing patient outcomes. Recent advances in real-time three dimensional (3D) echocardiography provide the option of real-time full volume color Doppler echocardiography (FVCD) measurements. This makes it practical to quantify MR by subtracting aortic stroke volume from the volume of mitral inflow in an automated manner.

METHODS

Thirty-two patients with more than a moderate degree of MR assessed by transthoracic echocardiography (TTE) were consecutively enrolled during this study. MR volume was measured by 1) two dimensional (2D) Doppler TTE, using the proximal isovelocity surface area (PISA) and the volumetric quantification methods (VM). Then, 2) real time 3D-FVCD was subsequently obtained, and dedicated software was used to quantify the MR volume. MR volume was also measured using 3) phase contrast cardiac magnetic resonance imaging (PC-CMR). In each patient, all these measurements were obtained within the same day. Automated MR quantification was feasible in 30 of 32 patients.

RESULTS

The mean regurgitant volume quantified by 2D-PISA, 2D-VM, 3D-FVCD, and PC-CMR was 72.1 ± 27.7, 79.9 ± 36.9, 69.9 ± 31.5, and 64.2 ± 30.7 mL, respectively (p = 0.304). There was an excellent correlation between the MR volume measured by PC-CMR and 3D-FVCD (r = 0.85, 95% CI 0.70-0.93, p < 0.001). Compared with PC-CMR, Bland-Altman analysis for 3D-FVCD showed a good agreement (2 standard deviations: 34.3 mL) than did 2D-PISA or 2D-VM (60.0 and 62.8 mL, respectively).

CONCLUSION

Automated quantification of MR with 3D-FVCD is feasible and accurate. It is a promising tool for the real-time 3D echocardiographic assessment of patients with MR.

A novel fully automated method for mitral regurgitant orifice area quantification

Background

Effective regurgitant orifice area (EROA) in mitral regurgitation (MR) is difficult to quantify. Clinically it is measured using the proximal isovelocity surface area (PISA) method, which is intrinsically not automatable, because it requires the operator to manually identify the mitral valve orifice. We introduce a new fully automated algorithm, (“AQURO”), which calculates EROA directly from echocardiographic colour M-mode data, without requiring operator input.

Methods

Multiple PISA measurements were compared to multiple AQURO measurements in twenty patients with MR. For PISA analysis, three mutually blinded observers measured EROA from the four stored video loops. For AQURO analysis, the software automatically processed the colour M-mode datasets and analysed the velocity field in the flow-convergence zone to extract EROA directly without any requirement for manual radius measurement.

Results

Reproducibility, measured by intraclass correlation (ICC), for PISA was 0.80, 0.83 and 0.83 (for 3 observers respectively). Reproducibility for AQURO was 0.97. Agreement between replicate measurements calculated using Bland-Altman standard deviation of difference (SDD) was 21,17 and 17mm²for the three respective observers viewing independent video loops using PISA. Agreement between replicate measurements for AQURO was 6, 5 and 7mm²for automated analysis of the three pairs of datasets.

Conclusions

By eliminating the need to identify the orifice location, AQURO avoids an important source of measurement variability. Compared with PISA, it also reduces the analysis time allowing analysis and averaging of data from significantly more beats, improving the consistency of EROA quantification.

AQURO, being fully automated, is a simple, effective enhancement for EROA quantification using standard echocardiographic equipment.

Direct measurement of proximal isovelocity surface area by real-time three-dimensional color Doppler for quantitation of aortic regurgitant volume: an in vitro validation

OBJECTIVE

The proximal isovelocity surface area (PISA) method is useful in the quantitation of aortic regurgitation (AR). We hypothesized that actual measurement of PISA provided with real-time 3-dimensional (3D) color Doppler yields more accurate regurgitant volumes than those estimated by 2-dimensional (2D) color Doppler PISA.

METHODS

We developed a pulsatile flow model for AR with an imaging chamber in which interchangeable regurgitant orifices with defined shapes and areas were incorporated. An ultrasonic flow meter was used to calculate the reference regurgitant volumes. A total of 29 different flow conditions for 5 orifices with different shapes were tested at a rate of 72 beats/min. 2D PISA was calculated as 2pi r(2), and 3D PISA was measured from 8 equidistant radial planes of the 3D PISA. Regurgitant volume was derived as PISA x aliasing velocity x time velocity integral of AR/peak AR velocity.

RESULTS

Regurgitant volumes by flow meter ranged between 12.6 and 30.6 mL/beat (mean 21.4 +/- 5.5 mL/beat). Regurgitant volumes estimated by 2D PISA correlated well with volumes measured by flow meter (r = 0.69); however, a significant underestimation was observed (y = 0.5x + 0.6). Correlation with flow meter volumes was stronger for 3D PISA-derived regurgitant volumes (r = 0.83); significantly less underestimation of regurgitant volumes was seen, with a regression line close to identity (y = 0.9x + 3.9).

CONCLUSION

Direct measurement of PISA is feasible, without geometric assumptions, using real-time 3D color Doppler. Calculation of aortic regurgitant volumes with 3D color Doppler using this methodology is more accurate than conventional 2D method with hemispheric PISA assumption.

Perioperative transesophageal echocardiographic evaluation of the native mitral valve

During the past few decades, the effect of intraoperative transesophageal echocardiography's (TEE) influence on perioperative cardiac surgical decision making has become increasingly more appreciated. To date, there are no prospective, large-scale, randomized trials that have specifically identified a consistent, independent advantage for intraoperative TEE. However, data from several clinical investigations have consistently implicated an important, clinically significant, and cost-effective role for TEE as a safe and valuable hemodynamic monitor in identifying high-risk patients, in assisting in the determination of the definitive surgical approach, and in providing a timely post-cardiopulmonary bypass evaluation of the procedure, thereby allowing for the opportunity to immediately re-intervene or to at least triage patients appropriately. In addition, intraoperative TEE has been instrumental in diagnosing cardiac and associated great vessel pathology and in identifying structural abnormalities, including the presence and extent of congenital abnormalities, aortic disease, intracardiac masses, and pericardial disease. Intraoperative TEE, however, has perhaps been most useful for the perioperative evaluation of cardiac valvular disease, especially during surgical procedures involving the mitral valve. This article will focus primarily on the role of intraoperative TEE in defining mitral valve anatomy, the pathogenesis and mechanism of mitral valve pathology, and its influence on perioperative clinical decision making in patients undergoing mitral valve surgery.

Assessment of functional anatomy of the mitral valve in patients with mitral regurgitation with cine magnetic resonance imaging: comparison with transesophageal echocardiography and surgical results

The ability of magnetic resonance imaging (MRI) to accurately define the functional anatomy of mitral regurgitation was assessed. Transesophageal echocardiography (TEE) and cine MRI were performed on 43 patients with mitral regurgitation and were compared for the jet number, location, direction and presence of a prolapse (atrial displacement, malapposition or a flail). In 36 patients, diagnostic accuracy in reference to surgery was assessed. Comparing TEE and MRI the jet number and location were judged in concordance in 86% of patients. Jet location did not show a significant difference (Wilcoxon: P = 0.66) and both modalities correlated strongly (Spearman: r = 0.68, P<0.0001). Jet direction was judged with high concordance (kappa=0.63). Additionally, prolapse evaluation showed high concordance (kappa: valve, 0.63; anterior mitral leaflet, 0.70; posterior mitral leaflet, 0.73). Compared with surgery, the sensitivity for the detection of malapposition of any leaflet or one of both leaflets ranged between 75% and 93% for TEE and 71% and 89% for MRI. Specificities ranged between 88 and 96% for TEE and 88 and 100% for MRI. TEE detected torn chordae in all ten patients, six of which were missed by MRI. MRI is comparable with TEE in prolapse and jet evaluation. MRI is inferior to TEE in depicting anatomical details such as torn chordae.

Assessment of left ventricular function by cardiac ultrasound

Our understanding of the physical underpinnings of the assessment of cardiac function is becoming increasingly sophisticated. Recent developments in cardiac ultrasound permit exploitation of many of these newer physical concepts with current echocardiographic machines. This review will first focus on the current approach to the assessment of cardiovascular hemodynamics by cardiac ultrasound. The next focus will be the assessment of global cardiac mechanics in systole and diastole. Finally, relationships between the cardiac structure and regional myocardial function, and the way regional function can be quantified by ultrasound, will be presented. This review also discusses the clinical impact of echocardiography and its future directions and developments.

Value of mitral valve tenting volume determined by real-time three-dimensional echocardiography in patients with functional mitral regurgitation

This study sought to evaluate mitral valve tenting volume (TnV) as a clinical parameter using real-time 3-dimensional echocardiography in patients with functional mitral regurgitation (MR). In 27 patients with functional MR and 4 controls without mitral disease, real-time 3-dimensional echocardiographic images were obtained to measure TnV frame by frame from presystole to end-systole. The maximal and minimal TnVs during systole were identified in each patient, and mitral annular areas and tenting heights were also measured. Using 2-dimensional echocardiography, tenting area (TnA) was measured from the apical long-axis, apical 4-chamber, and apical 2-chamber views. The regurgitant orifice area was measured by the proximal isovelocity surface area method. Maximal and minimal TnVs occurred at the time of 2 +/- 6% and 78 +/- 6% of whole systolic duration, respectively, and the systolic percentage change of TnV was related to that of tenting height but not to that of mitral annular area. TnA on the long-axis images was significantly larger than that on the 4- and 2-chamber images (2.5 +/- 1.4 vs 1.7 +/- 1.3 and 1.9 +/- 1.4 cm(2), respectively, p <0.001). Regurgitant orifice area was significantly correlated with maximal TnV (r = 0.90), minimal TnV (r = 0.86), and TnA on the long-axis (r = 0.79), 4-chamber (r = 0.75), and 2-chamber (r = 0.73) images. Among minimal TnV and 3 TnAs, minimal TnV was the only independent determinant of regurgitant orifice area (p <0.001). Minimal TnV >or=3.90 ml identified significant functional MR with a sensitivity of 86% and a specificity of 100%. In conclusion, TnV derived from real-time 3-dimensional echocardiography is a preferable novel single index for assessing mitral valve tethering in functional MR to TnA that is dependent on the location of 2-dimensional planes.

Determinants of Ischemic Mitral Regurgitation in Patients with Chronic Anterior Wall Myocardial Infarction: A Real Time Three-Dimensional Echocardiography Study

OBJECTIVE

We sought to elucidate the geometric determinants of ischemic mitral regurgitation (IMR) in patients with chronic anterior myocardial infarction (MI).

MATERIALS AND METHODS

In 16 patients with anterior MI only (Group A) and 18 patients with both anterior and inferoposterior MI (Group B), three parallel equidistant anteroposterior (AP) planes (medial, central, lateral) perpendicular to the mitral valvular commissure-commissure plane were generated. The systolic tenting area of the mitral valve (MVTa) and the angles between the annular plane and leaflets (anterior, Aalpha; posterior, Palpha) on the AP planes were measured. The left ventricular end-systolic and end-diastolic volumes, and end-diastolic and end-systolic mitral annular area (MAAs) were obtained.

RESULT

The regurgitant orifice area (ROA) was significantly smaller in Group A than Group B (0.08 +/- 0.09 vs 0.20 +/- 0.18 cm(2), P < 0.05). In the total of 34 patients, the medial MVTa (P < 0.001), MAAs (P < 0.05) and the spherical index (P < 0.05) were three independent determinants of ROA while the left ventricular volumes were not. MAAs was the only independent determinant of ROA in Group A, while the medial MVTa was in Group B. Palpha (P < 0.05) and MVTa (P = 0.06) tended to be larger in the medial than the lateral side in Group B, while no differences were found in Group A.

CONCLUSION

The geometry of the mitral valve apparatus was more important than the left ventricular volumes in determining the severity of IMR in patients with anterior MI. The posteromedial side tenting could play a critical role in causing significant IMR when the inferoposterior MI coexists with anterior MI.

Value of the proximal flow convergence method for quantification of the regurgitant volume in mitral regurgitation Influence of the mechanism of regurgitation, the imaging of the flow convergence region, and different calculation modalities

The purpose of this study was to evaluate whether the underlying mechanism of mitral regurgitation influences the reliability of the proximal flow con- vergence method to assess the regurgitant volume. Furthermore, the mode of imaging the flow convergence region and different correction algorithms for calculation of the regurgitant volume were compared.

METHODS

Regurgitant volume was assessed in 45 patients (age 61+/-13 years) with organic (n=19) and functional (n=26) mitral regurgitation by the proximal flow convergence method for aliasing velocities between 14 and 64 cm/s using two-dimensional color Doppler imaging. Different correction and calculation algorithms were compared. In addition, regurgitant volume was determined using color Doppler M-mode for an aliasing velocity of 28 cm/s. The quantitative Doppler method was used as reference.

RESULTS

In organic mitral regurgitation correlation coefficients (mean differences) between the proximal flow convergence method and the reference method were 0.25-0.43/ 0.58-0.67 (46-111 ml/15-17 ml) before/after geometric correction of the regurgitant volume for the aliasing velocities investigated. The correlation coefficient (mean difference) using color Doppler M-mode imaging was 0.68 (85 ml). The corresponding values in functional mitral regurgitation were 0.74-0.88/0.74-0.88 (-5-8 ml/-7-5 ml) for two-dimensional color Doppler and 0.88 (-1 ml) for M-mode imaging.

CONCLUSIONS

The regurgitant volume was overestimated by the proximal flow convergence method in organic mitral regurgitation irrespective of the application of different correction algorithms or the use of color Doppler M-mode. A sufficiently reliable determination of the regurgitant volume by the proximal flow convergence method was possible in functional mitral regurgitation. In that case a simplified calculation of the regurgitant volume based on the proximal flow convergence method was feasible.

Stroke volume and mitral annular velocities

The aim of this study was to assess the impact of stroke volume (SV) on mitral annular velocities derived from tissue Doppler imaging (TDI). To this end, conventional echocardiographic variables and TDI derived mitral annular velocities (S', E', A') were obtained in 14 patients (pts) with increased SV (due to primary mitral (n=12) (ISV group)), in 41 pts with reduced SV (due to ischemic (n=27) or dilated cardiomyopathy (n=9) or hypertensive heart disease (n=5) (RSV group)) and 29 asymptomatic controls with normal SV (CON group). Systolic (S') and early diastolic (E') mitral annular velocities were elevated in the ISV group in the comparison to the CON group, but were significantly reduced in the RSV group. Late diastolic annular velocities (A') did not differ between the ISV and the CON group, but were lowest in the RSV group. On simple linear regression analysis, SV was significantly related to S' (r=0.74, p<0.001), to E' (r=0.74, p<0.001) and to A' (r=0.43, p<0.01). On multiple regression analysis, SV was a stronger independent predictor of S' and E' than conventional systolic or diastolic echocardiographic variables. Thus, stroke volume has a significant impact on TDI derived systolic (S') and early diastolic (E') mitral annular velocities. This should be considered, when TDI is used in the evaluation of LV performance or in the estimation of filling pressures.

Assessment of severity of mechanical prosthetic mitral regurgitation by transoesophageal echocardiography

OBJECTIVE

To evaluate the ability of colour Doppler transoesophageal echocardiography (TOE) to assess quantitatively prosthetic mitral valve insufficiency.

METHODS

47 patients were studied with multiplane TOE and cardiac catheterisation. Proximal jet diameter was measured as the largest diameter of the vena contracta. Regurgitant area was measured by planimetry of the largest turbulent jet during systole. Flow convergence zone was considered to be present when a localised area of increased systolic velocities was apparent on the left ventricular side of the valve prosthesis. Pulmonary vein flow velocity was measured at peak systole and diastole.

RESULTS

Mean (SD) proximal jet diameter was 0.63 (0.16) cm, with good correlation with angiographic grades (r = 0.83). Mean (SD) maximum colour jet area was 7.9 (2.5) cm2 (r = 0.69) with worse correlation if a single imaging plane was used for measurements (r = 0.62). The ratio of systolic to diastolic peak pulmonary flow velocity averaged 0.7 (1.3) cm (r = -0.66) with better correlation (r = -0.71) if patients with atrial fibrillation were excluded. Mean (SD) regurgitant flow rate was 168 (135) ml/s and regurgitant orifice area was 0.56 (0.43) cm2, with good correlation with angiography (r = 0.77 and r = 0.78, respectively).

CONCLUSIONS

TOE correctly identified angiographically severe prosthetic mitral regurgitation, mainly by the assessment of the flow convergence region and the proximal diameter of the regurgitant jet.

Reproducibility of the proximal flow convergence method in mitral and tricuspid regurgitation

BACKGROUND

The follow-up of patients with mitral and tricuspid regurgitation is important for their clinical treatment. We aimed to evaluate the reproducibility of the flow convergence method in mitral and tricuspid regurgitation.

METHODS

The proximal flow convergence region was imaged with color Doppler ultrasound scanning echocardiography in 83 patients with mitral regurgitation, tricuspid regurgitation, or both. Proximal isovelocity surface area radii for aliasing velocities of 27 to 29 cm/s and 41 to 43 cm/s were repeatedly measured by the same experienced investigator on different days and by experienced and less experienced investigators at 1 day.

RESULTS

In mitral regurgitation, the intraobserver variability rate was 0.2% +/- 13.5% (2.8% +/- 13.3%) and the interobserver variability was 0.1% +/- 13.8% (1.7% +/- 18.0%) for an aliasing velocity of 27 to 29 cm/s (41-43 cm/s). For the aliasing velocity of 27 to 29 cm/s (41-43 cm/s), the 95% ranges for change of the proximal isovelocity surface area radii were +/- 2.7 mm (+/- 1.8 mm) for measurements repeated by the same investigator and +/- 2.7 mm ( +/- 2.4 mm) for different investigators. Interobserver variability was independent of the investigators' experience. Similar data were achieved in tricuspid regurgitation.

CONCLUSIONS

The proximal flow convergence method is acceptably reproducible in mitral and tricuspid regurgitation independent of the investigators experience. For the aliasing velocity of 27 to 29 cm/s (41-43 cm/s), the proximal isovelocity surface area radius has to change for >2.7 (2.4) mm before an altered severity of mitral or tricuspid regurgitation in a single patient can be assumed.

Usefulness of tissue Doppler imaging for estimation of filling pressures in patients with primary or secondary pure mitral regurgitation

Mitral annular velocities derived from tissue Doppler (S', E', A') and left ventricular (LV) end-diastolic pressures were obtained in 11 patients with significant primary mitral regurgitation (MR), 26 patients with significant MR secondary to ischemic or dilated cardiomyopathy, and in 29 asymptomatic controls. The mitral E/E' ratio was related significantly to LV end-diastolic pressure in patients with secondary, but not in patients with primary MR. In patients with secondary MR, a mitral E/E' ratio >15 predicted an elevated LV end-diastolic pressure with a sensitivity of 80% and a specificity of 100%. Thus, the mitral E/E' ratio is a reliable estimate of filling pressures only in subjects with significant secondary, but not with significant, primary MR.

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.