Influence of incremental changes in heart rate on mitral flow velocity: assessment in lightly sedated, conscious dogs

To determine the effect of increasing heart rate on mitral flow velocity variables, the time constant of left ventricular isovolumic relaxation and the transmitral pressure gradient, 16 lightly sedated, conscious dogs were studied with Doppler echocardiography during incremental right atrial pacing (n = 16) or the administration of atropine (n = 8) or isoproterenol (n = 8). With increasing heart rate, similar changes were seen with all three interventions and included: 1) mitral flow velocity in early diastole and the early diastolic transmitral pressure gradient either changed minimally or did not change; 2) mitral flow velocity at the start of and as a result of atrial contraction progressively increased; 3) the "absolute" increase in mitral flow velocity and transmitral pressure gradient at atrial contraction demonstrated a biphasic response, initially decreasing as heart rate increased, but then increasing again when atrial contraction occurred in close proximity (less than 70 ms) to mitral valve opening; 3) mitral flow velocity at atrial contraction did not exceed mitral flow velocity in early diastole until atrial contraction was within 70 ms of mitral valve opening and the two velocity peaks were nearly fused; and 4) the largest transmitral pressure gradient and mitral flow velocity occurred at the fastest heart rates, when left atrial contraction preceded mitral valve opening. Major differences among methods included: 1) variable changes in PR interval (+14.2 +- 8.9 ms with atrial pacing versus -74 +/- 26 ms with isoproterenol at peak heart rate compared with baseline); 2) variable changes in the speed of left ventricular relaxation (-2.8 +/- 2.8 ms with pacing versus -7.6 +/- 2.4 ms with isoproterenol at peak rate); and 3) the heart rate at which equalization of mitral flow velocity in early diastole and mitral flow velocity at atrial contraction velocity occurred (128 +/- 12 beats/min with pacing versus 185 +/- 19 beats/min with isoproterenol). These results show that regardless of method, qualitatively similar changes in mitral flow velocity and transmitral pressure gradient occur as heart rate increases. However, for any given heart rate, mitral flow velocity variables and late diastolic pressure gradient can be markedly different, depending on whether atrial pacing, withdrawal of parasympathetic tone or sympathetic stimulation is the cause of the increase in heart rate. These differences among methods appear most related to their effect on PR interval and to a lesser extent the rate of letf ventricular isovolumic relaxation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Different mechanisms for diastolic mitral regurgitation illustrated by three comparative cases

Diastolic mitral regurgitation (DMR) has been reported in patients with AV block, aortic regurgitation, cardiomyopathies, and in patients with long filling periods in atrial tachyarrhythmias. The mechanism for DMR is a reversal in the atrioventricular gradient during diastole. However, because of its relatively low velocity, it may be difficult to diagnose noninvasively. We present three different cases of diastolic MR in 2:1 second-degree AV block, atrial flutter, and dilated cardiomyopathy, with different locations in diastole. Diastolic tricuspid regurgitation commonly accompanies DMR. Careful analysis of echocardiographical images related with online ECG is very important in order to delineate systolic and DMR, and their timing in systole and diastole.     

Diastolic mitral and tricuspid regurgitation by Doppler echocardiography in patients with atrioventricular block: new insight into the mechanism of atrioventricular valve closure

The purpose of this study was to prospectively determine the incidence of diastolic mitral and tricuspid regurgitation in atrioventricular (AV) block using Doppler echocardiography. The temporal relation between mitral and tricuspid diastolic insufficiency and the diastolic murmur recorded in patients with complete heart block was also investigated. Twenty-two consecutive patients with AV block (referred to the Echo-Doppler laboratory for routine clinical studies), aged 18 to 87 years, were enrolled in the study. Eleven patients had third degree AV block and a ventricular-inhibited (VVI) pacemaker, two patients had second degree AV block, seven patients had first degree AV block, one patient had blocked premature atrial complexes and one patient had atrial flutter with 4:1 AV block. Diastolic mitral regurgitation was detected in 20 patients, and diastolic tricuspid regurgitation in 21. A mid-diastolic murmur was detected in all patients except in the three youngest. The murmur occurred before diastolic regurgitation and coincided with peak forward flow through the AV valve after atrial contraction. M-mode mitral valve echocardiograms obtained in nine patients demonstrated near closure of some portions of the mitral valve after atrial contraction. Effective closure of the valve, however, did not occur unless ventricular systole supervened. In conclusion, diastolic mitral and tricuspid regurgitation are almost universally present in patients with AV block and are associated with a diastolic murmur. The murmur coincides with forward AV valve flow. Diastolic regurgitation is silent. Effective AV valve closure is not established until ventricular systole occurs, as demonstrated by M-mode echocardiographic recording of the mitral valve.     

Experimental pericardial effusion: relation of abnormal respiratory variation in mitral flow velocity to hemodynamics and diastolic right heart collapse

Pericardial effusion is associated with an abnormal increase in respiratory variation in mitral flow velocity. However, the relation of the changes in flow velocity to pericardial pressure, hemodynamics and two-dimensional echocardiographic findings is not established. Therefore, 11 sedated dogs with extensive hemodynamic instrumentation were studied with two-dimensional and Doppler echocardiography during four stages of progressively larger pericardial effusion. During all stages of effusion, respiratory variation in peak mitral flow velocity in early diastole and left ventricular isovolumetric relaxation time was increased compared with baseline (p less than 0.05). This increase was seen at the earliest stage of effusion (mean pericardial pressure 4.2 +/- 1.4 versus -0.8 +/- 0.9 mm Hg at baseline, p less than 0.05), and preceded the appearance of unequivocal diastolic right heart collapse in every dog. Maximal respiratory variation coincided with the appearance of right atrial collapse (mean pericardial pressure 7.1 +/- 2.4 mm Hg; mean inspiratory decrease in aortic pressure 9.5 +/- 2.6 mm Hg; mean aortic pressure 88.2 +/- 15.2 versus 102.2 +/- 11.2 mm Hg at baseline, p less than 0.05; and cardiac output 3.8 +/- 1.2 versus 5.5 +/- 1.3 liters/min at baseline, p less than 0.05), but did not increase at stages associated with more severe hemodynamic compromise. In addition, the respiratory changes in peak mitral flow velocity in early diastole were associated with simultaneous changes in the diastolic transmitral pressure gradient. It is concluded that in this model of acute pericardial effusion 1) increased respiratory variation in early diastolic mitral flow velocity, peak mitral flow velocity in early diastole and left ventricular isovolumetric relaxation time occurs almost immediately as pericardial pressure increases and persists at all stages of increasing pericardial effusion; 2) the abnormal respiratory variation occurs before equalization of intracardiac pressures and before the onset of unequivocal right heart collapse; 3) the respiratory variation occurs as a result of changes in the diastolic transmitral pressure gradient; and 4) the magnitude of the respiratory change is not necessarily predictive of pericardial pressure or severity of hemodynamic compromise, especially at the more severe stages of pericardial effusion.     

Effects of preload reduction on mitral flow velocity pattern in normal subjects

In the last few years, alterations in transmitral diastolic flow pattern have been used to assess changes in left ventricular diastolic properties. However, since diastolic flow primarily reflects the atrioventricular pressure gradient, loading conditions, as well as intrinsic left ventricular properties, should be able to affect this pattern. This study was selectively designed to decrease preload (a major determinant of the atrioventricular pressure gradient) in normal subjects to observe the effects on the Doppler transmitral flow pattern without pharmacologic interventions that may also affect left ventricular diastolic properties. In 12 normal subjects, preload was reduced by inflation of blood pressure cuffs placed at the level of the root of the 4 limbs. The peak velocity of early mitral flow (E wave) decreased from 62 +/- 8 to 51 +/- 7 cm/s (p less than 0.001), while no changes were found in the maximal velocity after atrial contraction; this caused a significant decrease in the ratio of these 2 velocities (the E to A ratio) from 1.5 +/- 0.3 to 1.1 +/- 0.1 (p less than 0.001). The time-velocity integral of early diastolic inflow decreased from 7.8 +/- 1.3 to 6.1 +/- 1.3 cm (p less than 0.001) with no significant changes of the time-velocity integral of inflow after atrial contraction. Therefore, preload reduction in normal subjects significantly reduces transmitral flow in early diastole with preserved late ventricular filling, producing a pattern that can mimic the changes previously described in left ventricular diastolic dysfunction.     

Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling

OBJECTIVES: We hypothesized that color M-mode (CMM) images could be used to solve the Euler equation, yielding regional pressure gradients along the scanline, which could then be integrated to yield the unsteady Bernoulli equation and estimate noninvasively both the convective and inertial components of the transmitral pressure difference. BACKGROUND: Pulsed and continuous wave Doppler velocity measurements are routinely used clinically to assess severity of stenotic and regurgitant valves. However, only the convective component of the pressure gradient is measured, thereby neglecting the contribution of inertial forces, which may be significant, particularly for nonstenotic valves. Color M-mode provides a spatiotemporal representation of flow across the mitral valve. METHODS: In eight patients undergoing coronary artery bypass grafting, high-fidelity left atrial and ventricular pressure measurements were obtained synchronously with transmitral CMM digital recordings. The instantaneous diastolic transmitral pressure difference was computed from the M-mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation and was compared to the catheter measurements. RESULTS: From 56 beats in 16 hemodynamic stages, inclusion of the inertial term ([deltapI]max = 1.78+/-1.30 mm Hg) in the noninvasive pressure difference calculation significantly increased the temporal correlation with catheter-based measurement (r = 0.35+/-0.24 vs. 0.81+/-0.15, p< 0.0001). It also allowed an accurate approximation of the peak pressure difference ([deltapc+I]max = 0.95 [delta(p)cathh]max + 0.24, r = 0.96, p<0.001, error = 0.08+/-0.54 mm Hg). CONCLUSIONS: Inertial forces are significant components of the maximal pressure drop across the normal mitral valve. These can be accurately estimated noninvasively using CMM recordings of transmitral flow, which should improve the understanding of diastolic filling and function of the heart.     

Detection of a pseudonormal mitral inflow pattern: an echocardiographic and tissue Doppler study

OBJECTIVE: The aim of this study was to assess the ability of several echocardiographic and tissue Doppler imaging (TDI) derived parameters to improve the noninvasive diagnosis of a pseudonormal mitral inflow pattern. METHODS: Ninety-eight consecutive patients with age-related normal transmitral Doppler profile underwent echocardiography including TDI and measurement of left ventricular end-diastolic pressure (LVEDP) using fluid-filled catheters. Peak transmitral velocities were determined at rest (E, A) and during the strain phase of a Valsalva maneuver. The difference in duration between the pulmonary venous retrograde velocity and the transmitral A-velocity (PVR-A) was calculated from pulsed Doppler recordings. Propagation velocity of the early mitral inflow (VP) was determined by color M-mode. Early diastolic peak mitral annulus velocities (E') and the early diastolic transmyocardial velocity gradient of the posterior basal wall (MVG) were obtained by TDI. RESULTS: Fifty-two patients presented with normal diastolic function (group I: LVEDP9.5 +/- 3 mm Hg, E/A1.1 +/- 0.19), while pseudonormalization, defined as LVEDP 15 mm Hg and E/A > 0.9, was found in 46 patients (group II: LVEDP23 +/- 7 mm Hg, E/A1.43 +/- 0.83). The coefficient of linear correlation (r) and the area under ROC - curve (AUC) to predict LVEDP values 15 mm Hg were maximal for the index PVR-A (AUC = 0.92, r = 0.77), followed byE/E' (AUC = 0.80, r = 0.46), MVG (AUC = 0.65, r = 0.33) and E/VP (AUC = 0.69, r = 0.30), P < 0.01, whereas the decrease in E/A ratio during Valsalva maneuver failed to reach significance. Similar results were observed when echocardiographic parameters were used to estimate the left ventricular diastolic pressure before atrial contraction. CONCLUSIONS: PVR-A enabled the most accurate estimation of LVEDP. TDI-derived indices E/E' and MVG are also reliable alternatives superior to the classical Valsalva maneuver to detect a pseudonormal transmitral Doppler profile.     

Transmitral pressure-flow velocity relation. Importance of regional pressure gradients in the left ventricle during diastole

Effects of regional diastolic pressure differences within the left ventricle on the measured transmitral pressure-flow relation were determined by simultaneous micromanometric left atrial (LAP) and left ventricular pressure (LVP) measurements, and Doppler echocardiograms in 11 anesthetized, closed-chest dogs. Intraventricular pressure recordings at sites that were 2, 4, and 6 cm from the apex were obtained. Profound differences between these sites were noted in the transmitral pressure relation during early (preatrial) diastolic filling. In measurements from apex to base, minimum LVP increased (1.6 +/- 0.7 to 3.1 +/- 0.8 mm Hg, mean +/- SD); the time interval between the first crossover of transmitral pressures and minimum LVP increased (31 +/- 3 to 50 +/- 17 msec); the slope of the rapid-filling LVP wave decreased (74 +/- 13 to 26 +/- 5 mm Hg/sec); the maximum forward (i.e., LAP greater than LVP) transmitral pressure gradient decreased (3.6 +/- 1.3 to 2.1 +/- 0.7 mm Hg); the time interval between the first and second points of transmitral pressure crossover increased (71 +/- 9 to 96 +/- 13 msec); and the area of reversed (i.e., LVP greater than LAP) gradient between the second and third points of transmitral pressure crossover decreased (101 +/- 41 to 40 +/- 33 mm Hg.msec). During atrial contraction, significant regional ventricular apex-to-base gradients were also noted. The slope of the LV A wave decreased (26 +/- 10 to 16 +/- 4 mm Hg/sec); LV end-diastolic pressure decreased (8.1 +/- 2.0 to 7.4 +/- 2.0 mm Hg), and the upstroke of the LV A wave near the base was recorded earlier than near the apex. All differences were significant at the 0.05 level. Simultaneous transmitral Doppler velocity profiles and transmitral pressures were measured at the 4-cm intraventricular site. The average interval between the first and second points of pressure crossover and between the onset of early rapid filling and maximum E-wave velocity were statistically similar (81 +/- 13 vs. 85 +/- 12 msec; NS); and the average area of the forward transmitral pressure gradient associated with acceleration of early flow was significantly greater than the area of reversed gradient associated with deceleration of early flow (133 +/- 36 vs. 80 +/- 46 msec.mm Hg; p less than 0.025).(ABSTRACT TRUNCATED AT 400 WORDS)     

Pulmonary capillary wedge pressure in mitral stenosis accurately reflects mean left atrial pressure but overestimates transmitral gradient

Current opinion varies as to whether pulmonary capillary wedge pressure assessment of transmitral gradient in mitral stenosis is accurate; we therefore compared transmitral gradient in 36 patients awaiting balloon valvuloplasty using both pulmonary capillary wedge pressure and direct left atrial pressure. Mean pulmonary capillary wedge pressure correlated well with mean left atrial pressure (limits of agreement -1.5 to +3.7 mm Hg), but mean diastolic mitral gradient calculated using pulmonary capillary wedge pressure differed significantly from that calculated using left atrial pressure (limits of agreement -1.2 to +9.8 mm Hg): wedge pressure-assessed transmitral gradient is therefore misleading, routinely overestimating stenosis severity.     

Effect of nitroglycerin during hemodynamic estimation of valve orifice in patients with mitral stenosis

In patients with mitral stenosis, valve orifice calculations using pulmonary capillary wedge pressure as a substitute for left atrial pressure may overestimate the severity of disease. Previous studies have shown that mitral valve area determined from transseptal left atrial pressure measurements exceeds that area derived from pulmonary wedge pressure measurements. This is probably due to pulmonary venoconstriction, which is reversed by nitroglycerin. Nitroglycerin, 0.4 mg, was administered sublingually to 20 patients with mitral valve disease during preoperative cardiac catheterization using the pulmonary capillary wedge pressure as the proximal hydraulic variable. At the time of a peak hypotensive effect, 3 to 5 minutes after nitroglycerin administration, the mean pulmonary capillary wedge pressure decreased from 23 +/- 2 (mean +/- SEM) to 19 +/- 2 mm Hg (p less than 0.005). The mean diastolic transmitral pressure gradient (12.6 +/- 1.2 mm Hg before and 11.5 +/- 1.0 mm Hg after nitroglycerin; p = NS) and cardiac output (4.0 +/- 0.3 to 4.1 +/- 0.3 liters/min; p = NS) did not change significantly. Nevertheless, the hemodynamic mitral orifice area, calculated using the Gorlin formula, increased from 0.8 +/- 0.1 to 1.1 +/- 0.2 cm2 (p less than 0.05). In 12 patients with isolated mitral stenosis, without regurgitation, the mitral valve orifice area after nitroglycerin was 0.4 +/- 0.2 cm2 larger than it was before drug administration (p less than 0.05). Administration of nitroglycerin during evaluation of mitral stenosis eliminates pulmonary venoconstriction, which raises the pulmonary capillary wedge pressure above the left atrial pressure in some patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Doppler echocardiographic evaluation of ring mitral valvuloplasty for pure mitral regurgitation

Doppler echocardiographic studies were performed in 21 consecutive patients (mean age 56 +/- 11 years) to evaluate postoperative results of mitral ring anuloplasty. All patients were symptomatic and all had clinically severe isolated mitral regurgitation (MR). The origin of MR was myxomatous degeneration, coronary artery disease, rheumatic heart disease or congestive cardiomyopathy. In 20 patients ring anuloplasty was performed using the Carpentier ring and 1 patient using the Duran ring. Postoperative Doppler echocardiographic studies were performed to detect and semiquantitate residual MR by flow mapping and to identify left ventricular inflow or outflow obstruction. The severity of MR was assessed by flow mapping in the left atrium and graded from I to IV in increasing severity. Blood flow velocity spectra were recorded from the left ventricular outflow tract during systole and from the left ventricle subjacent to the mitral valve during diastole. Pressure half-time, mitral valve area and mitral valve gradient were derived from digitized mitral diastolic flow velocity spectra. After ring valvuloplasty, 9 patients had no MR and 6 had grade I, 3 grade II, 2 grade III and 1 patient grade IV MR. Peak diastolic mitral valve gradient was 8 +/- 4 mm Hg, mean diastolic gradient was 3 +/- 2 mm Hg and pressure half-time was 83 +/- 17 ms, representing a calculated mean mitral valve area of 2.9 +/- 0.8 cm. Peak velocity in the left ventricular outflow tract was 0.9 +/- 0.2 m/s, indicating no obstruction to outflow. Our study confirms that mitral ring valvuloplasty produces a significant reduction in severity of MR, and this is achieved without obstructing left ventricular inflow or outflow.     

Pressure-flow relations across the normal mitral valve

The stenotic mitral valve area is a major determinant of the atrioventricular pressure-flow relation, and mean atrioventricular pressure gradient is proportionate to the square of mean flow rate. In the absence of obstruction, this relation is linear. The effect of the normal mitral valve area on this pressure-flow relation has not been previously examined. Pulsed Doppler studies of transmitral flow were performed simultaneously with thermodilution cardiac outputs in 25 patients in sinus rhythm and with no valvular disease. Mean flow rate was determined as thermodilution stroke volume/diastolic filling period measured by Doppler. Several instantaneous pressure gradients were estimated from multiple velocity measurements using the modified Bernoulli equation and were plotted against time. Mean pressure gradient was estimated by dividing the area under the pressure-time curve by the diastolic filling period. Average and standard deviation of mean flow rate and pressure gradient was 223 +/- 70 ml/s and 1.4 +/- 0.8 mm Hg, respectively. There was an excellent linear correlation between these 2 parameters (r = 0.91, SEE = 30 ml/s). This confirms the linear relation of mean pressure gradient to mean flow rate in the absence of obstruction. The excellent correlation, obtained without considerations of individual variations of valve area, suggests that this relation is independent of valve area, under normal physiologic conditions.     

Effects of exercise on transmitral gradient and pulmonary artery pressure in patients with mitral stenosis or a prosthetic mitral valve: a Doppler echocardiographic study

Doppler echocardiography was used to determine changes in transmitral gradient and pulmonary artery pressure after exercise in 12 patients with mitral stenosis and 11 patients with a prosthetic mitral valve. The mean transmitral gradient in the mitral stenosis group was 9 +/- 7 mm Hg at rest and increased to 17 +/- 8 mm Hg after exercise. In patients with a prosthetic mitral valve, exercise resulted in an increase in mean transmitral gradient from 5 +/- 2 to 8 +/- 3 mm Hg. Calculated pulmonary artery systolic pressure increased with exercise from 41 +/- 19 to 70 +/- 32 mm Hg in the mitral stenosis group and from 28 +/- 8 to 39 +/- 15 mm Hg in patients with a prosthetic valve. Exercise Doppler echocardiographic evaluation of changes in transmitral gradient and pulmonary artery systolic pressure was found to be technically simple and an important addition to the noninvasive evaluation of patients with mitral valve disease.     

Doppler echocardiographic comparison of the Carpentier and Duran anuloplasty rings versus no ring after mitral valve repair for mitral regurgitation

To compare the hemodynamic results of different anuloplasty techniques of primary valve repair for mitral regurgitation, 122 patients were prospectively studied with Doppler echocardiograms 5 to 10 days after operation. Seventy-seven patients had mitral valve prolapse, 27 had coronary artery disease, 13 patients had rheumatic mitral valve lesions and 5 patients had infective endocarditis. Forty-eight patients received the flexible Duran ring, 46 received the more rigid Carpentier ring and 28 patients received no ring. Doppler echocardiography demonstrated a significant decrease in mitral valve area estimated by the pressure half-time method in patients who received either a Carpentier (2.6 +/- 0.8 cm2) or Duran ring (2.8 +/- 0.8 cm2) when compared with patients who received no ring (3.2 +/- 0.7 cm2) (p = 0.01). No significant differences were observed for peak transmitral diastolic velocity, peak transmitral diastolic gradient, or the grade of mitral regurgitation by color flow Doppler mapping between patients with and without rings. The etiology of mitral disease and concomitant surgical procedures accompanying mitral valve repair did not significantly influence mitral valve area, peak velocity or peak gradient. These data suggest that Carpentier and Duran rings decrease the hemodynamic mitral valve area; however, the decrease in valve area is small and not associated with a clinically important increase in transvalvular gradient.     

Valvular regurgitation in patients with complete heart block by color Doppler echocardiography

We studied valvular regurgitation (pulmonary, aortic, tricuspid and mitral regurgitation) in 30 patients with complete heart block by color Doppler echocardiography, pulse Doppler and continuous wave Doppler echocardiography. The prevalence rate of multivalvular regurgitation of these subjects was 83.3%. Regurgitation involving all four valves appeared in 30.0% of these patients. The prevalence rate of pulmonary, aortic, tricuspid and mitral regurgitation was 56.7%, 33.3%, 100%, and 76.7% respectively. Pulmonary regurgitation (PR) was observed in patients with complete heart block without pulmonary hypertension. PR velocity was slow and interrupted by atrial contraction. It might be possible to evaluate atrial pressure from the interruption of PR. Tricuspid regurgitation (TR) during systole was often present in patients with right ventricular endocardial pacing. Systolic TR was influenced by atrial contraction. When atrial contraction occurred during systole, TR was interrupted, or shortened. Diastolic TR and MR were easily detected by M mode color Doppler echocardiography. The diastolic TR and MR were of slow velocity and appeared 240-290 msec after P wave. These atypical valvular regurgitation in patients with complete heart block reflect of the inverse atrial-ventricular pressure gradient across the atrio-ventricular valve.     

Efficacy of atrioventricular sequential pacing and diastolic mitral regurgitation in patients with intrinsic atrioventricular conduction

The efficacy of a short atrioventricular (AV) delay in patients with dilated cardiomyopathy has been reported, but there are deleterious effects of right ventricular pacing. Diastolic mitral regurgitation (MR) is observed in patients with elevated left ventricular end-diastolic pressure and can be induced by prolonging the AV delay in patients with DDD pacemakers. The critical PQ interval that induces diastolic MR may represent the upper limit of the optimal PQ interval. The efficacy of AV sequential pacing and diastolic MR were studied in 11 patients (68.3+/-13.7 (SD) years old) with intrinsic AV conduction and with implanted DDD pacemakers. Cardiac output (CO) and pulmonary capillary wedge pressure (PCWP) were measured by Swan-Ganz catheter and transmitral flow was recorded by pulsed Doppler echocardiography. AV delay was prolonged stepwise by 25 ms starting from 65 ms. Pacing rate was fixed at 70-80 beats/min. In 6 of the 11 patients, diastolic MR was observed under atrial pacing and the critical PQ interval for the appearance of diastolic MR was 0.22+/-0.04 s. CO was increased from 3.8+/-0.8 to 4.3+/-0.9 L/min (p<0.05) and PCWP was decreased from 7.5+/-2.8 to 5.5+/-1.6 mmHg (p<0.05) by shortening the AV delay till the diastolic MR disappeared. On the other hand, in 5 of the 11 patients, diastolic MR was not observed, and CO (4.2+/-0.5 to 4.3+/-0.5L/min, ns) and PCWP (5.8+/-4.6 to 5.4+/-3.9 mmHg, ns) were not improved by AV sequential pacing. In conclusion, cardiac function may be improved by AV sequential pacing and setting the AV delay under the critical PQ interval for the appearance of diastolic MR when the diastolic MR is observed. However, AV sequential pacing may be either ineffective or even deleterious for patients in whom diastolic MR is not observed.     

Doppler echographic evaluation of mitral valve stenosis with atrial fibrillation. Construction of a nomogram]

Doppler echocardiographic evaluation of mitral stenosis is often difficult in patients with atrial fibrillation. Sixteen patients were examined by transthoracic Doppler echocardiography and the relation between the variations in transmitral end diastolic pressure gradient and the length of the corresponding cardiac cycles was analysed. Mitral valve surface area (1.65 +/- 0.73 cm2) was determined by the pressure half-time method. The end diastolic transmitral pressure gradient was calculated from the simplified Bernouilli formula applied to end diastolic mitral flow velocity. In each patient, a linear relationship was observed between the end diastolic mitral gradient and the corresponding RR interval. The slope and intercept of the graph correlated significantly to mitral valve surface area (r = 0.72, p < 0.002 and r = 0.93, p < 0.00001, respectively). Using regression equations describing these correlations, it has been possible to construct a nomogramme indicating mitral valve surface area as a function of mitral end diastolic pressure gradient and the duration of the corresponding RR cycle. This nomogramme facilitates Doppler evaluation of mitral stenosis in atrial fibrillation.     

Acute effects of cardiac resynchronization therapy on functional mitral regurgitation in advanced systolic heart failure

OBJECTIVES: We studied the acute effects of cardiac resynchronization therapy (CRT) on functional mitral regurgitation in heart failure (HF) patients with left bundle branch block (LBBB). BACKGROUND: Both an decrease [corrected] in left ventricular (LV) closing force and mitral valve tethering have been implicated as mechanisms for functional mitral regurgitation (FMR) in dilated hearts. We hypothesized that an increase in LV closing force achieved by CRT could act to reduce FMR. METHODS: Twenty-four HF patients with LBBB and FMR were studied after implantation of a biventricular CRT system. Acute changes in FMR severity between intrinsic conduction (OFF) and CRT were quantified according to the proximal isovelocity surface area method by measuring the effective regurgitant orifice area (EROA). Results were compared with the changes in estimated maximal rate of left ventricular systolic pressure rise (LV+dP/dt(max)) and transmitral pressure gradients (TMP), both measured by Doppler echocardiography. RESULTS: Cardiac resynchronization therapy was associated with a significant reduction in FMR severity. Effective regurgitant orifice area decreased from 25 +/- 19 mm(2) (OFF) to 13 +/- 8 mm(2) (CRT). The change in EROA was directly related to the increase in LV+dP/dt(max) (r = -0.83, p < 0.0001). Compared with OFF, TMP increased more rapidly during CRT, and a higher maximal TMP was observed (OFF 73 +/- 24 mm Hg vs. CRT 85 +/- 26 mm Hg, p < 0.01). CONCLUSIONS: Functional mitral regurgitation is reduced by CRT in patients with HF and LBBB. This effect is directly related to the increased closing force (LV+dP/dt(max)). The results support the hypothesis that an increase in TMP, mediated by a rise in LV+dP/dt(max) due to more coordinated LV contraction, may facilitate effective mitral valve closure.     

Characterization of regional diastolic pressure gradients in the right ventricle

Regional intraventricular pressure gradients exist in the left ventricle (LV) during both the early and late filling phases of diastole. These regional pressure gradients comprise a fundamental component of the mechanism of normal LV filling. To determine whether similar diastolic pressure gradients also occur in the right ventricle (RV), we measured right atrial (RA) and RV regional pressures with use of micromanometers in six anesthetized, closed-chest dogs. Tricuspid flow velocity was recorded with use of transesophageal Doppler echocardiography, and right ventriculograms were obtained with contrast angiography. As in the LV, the maximum RA-RV pressure gradient during early diastole was consistently greater if RV pressure was measured near the apex than in the inflow tract (1.6 +/- 0.5 versus 0.8 +/- 0.4 mm Hg). The area of reversed pressure was also found to be significantly greater in the apex than in the inflow tract (72 +/- 43 versus 8 +/- 6 mm Hg.msec). However, unlike the LV, the lowest minimum pressure was usually recorded in the RV outflow tract, resulting in a significantly increased RA-RV outflow tract pressure gradient compared with the RA-RV apex pressure gradient (2.5 +/- 0.8 versus 1.6 +/- 0.5 mm Hg). Analysis of right ventriculograms indicates marked narrowing of the RV outflow tract at end systole in all six animals, suggesting that an end-systolic deformation in this region is the likely mechanism for production of low early diastolic pressure in this region. During atrial contraction the RV regional pressure gradient pattern was similar to the LV pattern: the RV a-wave ascent occurred earlier in the inflow tract and later in the apex. A-wave ascent appeared to occur almost simultaneously in the apex and outflow tract. In the six animals, Doppler-derived peak tricuspid flow velocity during early diastole was 35 +/- 6 cm/sec. Early tricuspid flow acceleration (393 +/- 101 cm/sec2) was found to be significantly greater than deceleration of flow (182 +/- 59 cm/sec2). Comparison of tricuspid pressure-flow data with mitral pressure-flow data previously obtained in our laboratory indicates that the driving pressure gradient across the tricuspid valve is significantly less than across the mitral. This pressure difference corresponds to differences in acceleration and peak flow found across the two valves. Consideration of these physiological patterns of RV diastolic intraventricular pressure and their relation to filling has important implications with regard to the development of indexes that characterize diastolic pressure-flow relations and provides physiological insight relating to the location of ventricular restoring forces.     

Fluid dynamics model of mitral valve flow: description with in vitro validation

A lumped variable fluid dynamics model of mitral valve blood flow is described that is applicable to both Doppler echocardiography and invasive hemodynamic measurement. Given left atrial and ventricular compliance, initial pressures and mitral valve impedance, the model predicts the time course of mitral flow and atrial and ventricular pressure. The predictions of this mathematic formulation have been tested in an in vitro analog of the left heart in which mitral valve area and atrial and ventricular compliance can be accurately controlled. For the situation of constant chamber compliance, transmitral gradient is predicted to decay as a parabolic curve, and this has been confirmed in the in vitro model with r greater than 0.99 in all cases for a range of orifice area from 0.3 to 3.0 cm2, initial pressure gradient from 2.4 to 14.2 mm Hg and net chamber compliance from 16 to 29 cc/mm Hg. This mathematic formulation of transmitral flow should help to unify the Doppler echocardiographic and catheterization assessment of mitral stenosis and left ventricular diastolic dysfunction.