Atriogenic diastoliceflux in patients with atrioventricular block

Diastolic mitral regurgitation following transcatheter aortic valve replacement: Incidence, predictors, and association with clinical outcomes

BACKGROUND

Diastolic mitral regurgitation (DMR) results from atrioventricular conduction disturbances, acute aortic regurgitation, and/or marked elevation of left ventricular filling pressure. Generally benign, in some clinical circumstances DMR has presumed to result in hemodynamic decompensation. The aforementioned causes of DMR are frequently encountered in patients treated by transcatheter aortic valve replacement (TAVR) but its clinical significance in this setting has not been studied. We sought to investigate the incidence of DMR and its prognostic implications following TAVR.

METHODS

Baseline clinical and echocardiographic variables from a prospective TAVR registry were analyzed to determine the correlates of post-procedural DMR and its impact on late outcomes (all-cause mortality and the composite of mortality and readmission due to heart failure).

RESULTS

Of 267 patients undergoing TAVR, post-procedural DMR was present in 25 (9.3%). Independent predictors of DMR included pacemaker implantation [OR=2.7 (95%CI 1.03-6.50)], post-procedural systolic MR and aortic regurgitation [OR=3.7 (1.20-10.80) and OR=4.1 (1.50-10.60), respectively], and use of self-expanding bioprostheses [OR=4.9 (1.60-21.0)]. The incidence of the combined endpoint of death and/or readmission for heart failure was higher in patients with versus those without DMR (25% vs. 41%, respectively, p=0.08), although this association did not attain statistical significance on multivariable analyses. Interaction term analysis indicated a trend toward a heightened risk for the composite endpoint among patients with post-procedural aortic regurgitation (≥moderate) in whom DMR occurred (χ² 2.94, p=0.09).

CONCLUSIONS

Although DMR following TAVR is common (occurring in approximately 1 of 10 patients), it is not independently associated with an increased risk of death and/or readmission for heart failure. Therefore, DMR post TAVR is more likely a marker of cardiac dysfunction than a causative factor.

Physiology of cardiac resynchronization

Dyssynchronous ventricular contraction, often associated with delayed electrical activation, contributes to worsened clinical status in patients with chronic dilated heart failure. There are three levels of impaired electromechanical synchrony that can be recognized and potentially improved with pacing methods. Prolonged atrioventricular (AV) delay can promote presystolic mitral regurgitation and impaired left ventricular (LV) filling. Interventricular conduction delay with right ventricular (RV) activation preceding LV activation often occurs in the setting of left bundle branch block or RV apical pacing, and can result in impeded LV filling and ejection. Activation delays within the LV itself (intraventricular dyssynchrony) can cause decreased efficiency of contraction, increased mitral regurgitation, and abnormal ventricular remodeling. Cardiac resynchronization therapy (CRT) can improve ventricular performance in two thirds of patients selected based on QRS duration alone. Improved understanding of the pathophysiology of cardiac dyssynchrony will aid in patient selection and in assessment and optimization of response to CRT.

Cardiac resynchronization therapy is certainly cardiac therapy, but how much resynchronization and how much atrioventricular delay optimization?

Cardiac resynchronization therapy has become a standard therapy for patients who are refractory to optimal medical therapy and fulfill the criteria of QRS >120 ms, ejection fraction <35% and NYHA class II, III or IV. Unless there is some other heretofore unrecognized effect of pacing, the benefits of atrio-biventricular pacing on hard outcomes observed in randomized trials can only be attributed to the physiological changes it induces such as increases in cardiac output and/or reduction in myocardial oxygen consumption leading to an improvement in cardiac function efficiency. The term “Cardiac Resynchronization Therapy” for biventricular pacing presupposes that restoration of synchrony (simultaneity of timing) between left and right ventricles and/or between walls of the left ventricle is the mechanism of benefit. But could a substantial proportion of these benefits arise not from ventricular resynchronization but from favorable shortening of AV delay (“AV optimization”) which cannot be termed “resynchronization” unless the meaning of the word is stretched to cover any change in timing, thus, rendering the word almost meaningless. Here, we examine the evidence on the relative balance of resynchronization and AV delay shortening as contributors to the undoubted clinical efficacy of CRT.

Novel method of predicting the optimal atrioventricular delay in patients with complete AV block, normal left ventricular function and an implanted DDD pacemaker

BACKGROUND

The optimal atrioventricular (AV) delay setting is important for achieving optimal AV synchrony in patients with an implanted DDD pacemaker. Using pulsed Doppler echocardiography is the most common method of predicting the optimal AV delay, but it is a complicated and time-consuming method. Therefore, an automatic optimizing function of the AV delay at different atrial rates is desirable for achieving a favorable hemodynamic state. This study aimed to predict the optimal AV delay using phonocardiography.

METHODS AND RESULTS

The amplitude of the first heart sound (S1) recorded on the phonocardiogram was measured with different AV delays in 6 patents with complete AV block, normal left ventricular function and an implanted DDD pacemaker. The correlation between the amplitude of S1 and the length of the AV delay was a cubic curve (y=974.15x(3)-23.084x(2)-8.0074x+0.7495, R2=0.9511). The length of the AV delay at the inflection point of the curve showed a significant positive correlation with the optimal AV delay determined by pulsed Doppler echocardiography (R=0.9254, P<0.01).

CONCLUSIONS

This study demonstrated a novel simple method of predicting the optimal AV delay using phono-cardiography.

First-degree atrioventricular block

Marked first-degree AV block (PR> or =0.30 s) can produce a clinical condition similar to that of the pacemaker syndrome. Clinical evaluation often requires a treadmill stress test because patients are more likely to become symptomatic with mild or moderate exercise when the PR interval cannot adapt appropriately. Uncontrolled studies have shown that many such symptomatic patients with normal left ventricular (LV) function improve with conventional dual chamber pacing (Class IIa indication). In contrast, marked first-degree AV block with LV systolic dysfunction and heart failure is still a Class IIb indication, a recommendation that is now questionable because a conventional DDD(R) pacemaker would be committed to right ventricular pacing (and its attendant risks) virtually 100% of the time. It would seem prudent at this juncture to consider a biventricular DDD device in this situation. Patients with suboptimally programmed pacemakers may develop functional atrial undersensing because the P wave tends to migrate easily into the postventricular atrial refractory period (PVARP). Retrograde vetriculoatrial conduction block is uncommon in marked first-degree AV block so a relatively short PVARP can often be used at rest with little risk of endless loop tachycardia. The usefulness of a short PVARP may be negated by special PVARP functions in some pulse generators designed to time out a long PVARP at rest and a gradually shorter one with activity. First-degree AV block during cardiac resynchronization therapy (CRT) predisposes to loss of ventricular resynchronization during biventricular pacing because it favors the initiation of electrical "desynchronization" especially in association with a relatively fast atrial rate and a relatively slow programmed upper rate. Patients with first-degree AV block have a poorer outcome with CRT than patients with a normal PR interval, a response that may involve several mechanisms. (1) The long PR interval may be a marker of more advanced heart disease. (2) Patients with first-degree AV block may experience more episodes of undetected "electrical desynchronization". (3) "Concealed resynchronization" whereupon ventricular activation in patients with a normal PR interval may result from fusion of electrical wavefronts coming from the right bundle branch and the impulse from the LV electrode. The resultant hemodynamic response may be superior because the detrimental effects of right ventricular stimulation (required in the setting of a longer PR interval) are avoided.

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.

Pacing in congestive heart failure

Despite the major advances in medical drug therapy, heart failure remains a syndrome associated with high mortality and morbidity. Biventricular or left ventricular (LV) short atrioventricular (AV) delay pacing is being tested in congestive heart failure patients with left bundle branch block. The aim is to resynchronise the dyscoordinate LV contraction. A number of studies are underway, but it is clear that while some patients respond remarkably, this is highly variable. Accurate identification of patients likely to benefit will be crucial. The mechanism of benefit is unclear. A greater understanding of the physiological consequences of pacing will be necessary to accurately identify these patients.

Prediction of optimal atrioventricular delay in patients with implanted DDD pacemakers

In patients with an implanted DDD pacemaker (PM), the atrial contribution may be interrupted by too short an atrioventricular (AV) delay, and filling time may be shortened by too long an AV delay. The AV delay at which the end of the A wave on transmitral flow coincides with complete closure of the mitral valve may be optimal. The subjects were 15 patients [70.3+/-12.3 (SD) years old] with an implanted DDD PM. Cardiac output (CO) and pulmonary capillary wedge pressure (PCWP) were measured by Swan-Ganz catheter. Transmitral flow was recorded by pulsed Doppler echocardiography. AV delay was prolonged stepwise by 25 msc. When the AV delay was set at 155+/-26 ms, the end of the A wave coincided with complete closure of the mitral valve. When the AV delay was prolonged 25, 50, 75, and 100 ms from this AV delay, the interval between the end of the A wave and complete closure of mitral the valve was prolonged 16+/-5, 39+/-6, 65+/-4 and 88+/-5 ms, respectively (r = 0.97, P<0.0001) and diastolic mitral regurgitation was observed during this period. Thus, the optimal AV delay may be predicted as follows: the slightly prolonged AV delay minus the interval between the end of the A wave and complete closure of the mitral valve. When the AV delay was set at 215 ms, there was a significant positive correlation between the predicted optimal AV delay (166+/-23 ms) and the optimal AV delay (CO: 161+/-26 msec, r = 0.93, P<0.0001, PCWP: 161+/-28 msec, r = 0.95, P<0.0001). In conclusion, optimal AV delay can be predicted by this simple formula: slightly prolonged AV delay minus the interval between end of A wave and complete closure of mitral valve at the AV delay setting.

Refractory Heart Failure: A Therapeutic Approach

Optimal “triple therapy” for patients with chronic congestive heart failure (CHF) includes diuretics, digoxin, and either angiotensin-converting enzyme inhibitors or hydralazine plus nitrates. Refractory CHF is defined as symptoms of CHF at rest or repeated exacerbations of CHF despite “optimal” triple-drug therapy. Most patients with refractory CHF require hemodynamic monitoring and treatment in the intensive care unit. If easily reversible causes of refractory CHF cannot be identified, then more aggressive medical and surgical interventions are necessary. The primary goal of intervention is to improve hemodynamics to palliate CHF symptoms and signs (i.e., dyspnea, fatigue, edema). Secondary goals include improved vital organ and tissue perfusion, discharge from the intensive care unit, and, in appropriate patients, bridge to cardiac transplantation. Medical interventions include inotropic resuscitation (e.g., adrenergic agents, phosphodiesterase inhibitors, allied nonglycoside inodilators), load resuscitation (e.g., afterload and preload reduction with nitroprusside or nitroglycerin; preload reduction with diuretics and diuretic facilitators, such as dopaminergic agents or ultrafiltration), and electrical resuscitation (e.g., prevention of sudden death, correction of new or rapid atrial fibrillation, or dual chamber pacing in the setting of relative prolongation of the PR interval and diastolic mitral/tricuspid regurgitation). Surgical interventions are temporizing (e.g., intra-aortic balloon pump and other mechanical assist devices) or definitive (e.g., coronary artery revascularization, valvular surgery, and cardiac transplantation). Although these interventions may improve immediate survival in the short term, only coronary artery revascularization and cardiac transplantation have been shown to improve long-term survival.

Colour flow Doppler echocardiography in normal horses

Colour flow Doppler echocardiography is a technique that is used with two-dimensional (2-D) echocardiography to study blood flow patterns in the heart and blood vessels. This method was used to define normal flow patterns and to evaluate valvular function in 40 clinically normal Thoroughbred and Thoroughbred cross horses. Flow patterns from 10 standardised echocardiographic images were described in relation to anatomic landmarks and timing during the cardiac cycle. Consistent intracardiac flow patterns were identified in the normal horses. High velocity flow signals or regurgitant jets were recorded at the tricuspid (77.5%), mitral (67.5%), aortic (47.5%) and pulmonary valves (40%) in clinically normal horses. Most of these signals were transient, and many were associated with valve closure. This study demonstrates that colour flow Doppler echocardiography is a sensitive technique for the detection of intracardiac flow in horses. It will provide a basis by which to compare studies in horses suspected of having valvular heart disease.

Mechanism of hemodynamic improvement by dual-chamber pacing for severe left ventricular dysfunction: an acute Doppler and catheterization hemodynamic study

OBJECTIVES

This study was undertaken to determine the mechanism by which improvement in hemodynamic variables may occur with dual-chamber pacing in patients with severe left ventricular dysfunction.

BACKGROUND

Dual-chamber pacing has recently been proposed as a therapeutic alternative for the relief of symptoms in patients with dilated cardiomyopathy.

METHODS

Fifteen patients with severe left ventricular systolic dysfunction were studied acutely during atrioventricular (AV) sequential pacing at various AV intervals (60, 100, 120, 140, 180 and 240 ms) with use of combined Doppler velocity curves and pressures obtained by high fidelity manometer-tipped catheters and thermodilution cardiac output.

RESULTS

Neither cardiac output nor mean left atrial pressure was significantly different when hemodynamic variables in the baseline state were compared with those during AV sequential pacing at the various AV intervals in all patients. The patients were classified into two groups. In group I (eight patients with PR intervals > 200 ms on the rest 12-lead electrocardiogram), cardiac output was significantly increased when AV sequential pacing at the optimal AV interval to output was compared with that at the baseline state (3.0 +/- 1.0 vs. 3.9 +/- 0.43 liters/min, p = 0.005) because timing of mechanical atrial and ventricular synchrony was optimized. In addition, left ventricular end-diastolic pressure and duration of diastolic filling were increased, and diastolic mitral regurgitation was abolished. In group II (seven patients who had normal AV conduction at rest), cardiac output during AV pacing decreased from the baseline value without change in the diastolic filling period.

CONCLUSIONS

Dual-chamber pacing may improve acute hemodynamic variables in selected patients with dilated cardiomyopathy, mainly by optimization of the timing of mechanical atrial and ventricular synchrony. Reestablishment of the optimal diastolic filling period and abolition of diastolic mitral regurgitation may also contribute to hemodynamic improvement.

Critical PQ interval for the appearance of diastolic mitral regurgitation and optimal PQ interval in patients implanted with DDD pacemakers

Diastolic mitral regurgitation (MR) may be induced by prolonging atrioventricular (AV) delay, and a significant negative correlation has been described between the critical PQ interval for the appearance of diastolic MR and pulmonary capillary wedge pressure (PCWP) in patients with DDD pacemakers. We report the relationship between the critical PQ interval for the appearance of diastolic MR and the optimal PQ interval in 11 patients (69.1 +/- 12.6 years). Cardiac output (CO) and PCWP were measured by Swan-Ganz catheter and transmitral blood flow was recorded by pulsed-Doppler echocardiography. AV delay was prolonged stepwise by 0.025 seconds starting from 0.065 seconds. The pacing rate was fixed at 70 beats/min. CO was highest when the PQ interval was 0.18 +/- 0.04 seconds. There was a significant positive correlation between the critical PQ interval for the appearance of diastolic MR and the PQ interval at which CO was the highest (r = 0.91, P < 0.01). The PQ interval at which CO was the highest was 0.02 +/- 0.02 seconds shorter than the critical PQ interval for the appearance of diastolic MR (P < 0.05). When the PQ interval was increased by 0.025 seconds from the critical PQ interval for the appearance of diastolic MR, CO decreased from 4.3 +/- 0.6 L/min to 4.1 +/- 0.6 L/min and PCWP increased from 7.5 +/- 6.4 mmHg to 8.5 +/- 7.3 mmHg (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma ANP and cyclic GMP levels versus left ventricular performance at different AV delays in AV sequential pacing

Eleven resting patients with an implanted DDD pacemaker were studied. After 30 minutes of AV sequential pacing at a rate of 80 beats/min with three consecutive atrioventricular delays (AVDs; 100, 150, and 200 msec) peripheral venous blood was drawn for further analyses by specific radioimmunoassays of atrial natriuretic peptide (ANP) and the ANP second messenger, cyclic guanosine monophosphate (cGMP). Relative changes in left ventricular (LV) stroke volume following alterations of AVD were assessed by means of pulsed-Doppler echocardiography through measurement of LV outflow time-velocity integrals (TVI). The optimal AVD (oAVD) was defined in individual patients as that which was associated with the greatest TVI and with improvement over both other AVDs of more than 4%. The oAVD was found in nine patients. For these nine patients no significant differences in either plasma ANP or cGMP between various AVDs were observed. However, we found such differences with respect to values measured at oAVD; both ANP and cGMP levels were lowest at oAVD. Pooling together the data obtained in 11 patients at three AVDs, a positive correlation between ANP and cGMP levels was found (r = 0.7, P < 0.0001, n = 33). Moreover, changes of plasma ANP and cGMP induced by every AVD increment of 50 msec were also correlated (r = 0.6, P < 0.01, n = 22). It is concluded that in AV sequential pacing at rest plasma ANP reaches minimal levels at the AVD, which provides the best LV performance. Although levels of cGMP changed in parallel with those of ANP, low relative values of cGMP differences may limit the usefulness of cGMP assays in optimization of the AVD.

Effects of dual-chamber pacing with short atrioventricular delay in dilated cardiomyopathy

Mitral or tricuspid regurgitation of long duration may so shorten the ventricular filling time in dilated cardiomyopathy that stroke volume is limited. We assessed the effects of changing the atrioventricular interval during temporary or permanent dual-chamber DDD pacing in twelve dilated cardiomyopathy patients with short ventricular filling times due to regurgitation. We measured ventricular filling time and cardiac output with doppler echocardiography and exercise capacity on a treadmill, at baseline and with the best atrioventricular delay during pacing. The durations of both mitral and tricuspid regurgitation were significantly shorter at the shorter atrioventricular interval (mean reductions 85 [95% CI 60-110] ms and 110 [75-150] ms, respectively; p < 0.001 for both). There were consequent increases in left-ventricular and right-ventricular filling times (65 [35-95] ms and 90 [60-120] ms, p < 0.001). For each 50 ms reduction in atrioventricular delay, left-ventricular filling time increased by 35 ms in six subjects with presystolic mitral regurgitation and right-ventricular filling time by 30 ms in nine subjects with presystolic tricuspid regurgitation. At the short atrioventricular interval, cardiac output was greater than baseline (by 1.1 [0.8-1.4] l/min, p < 0.01) and there were rises in exercise duration (104 [45-165] s, p < 0.05) and maximum oxygen consumption (2.1 [1.5-2.7] ml kg-1 min-1, p < 0.05). There was a decrease in the Likert visual analogue score of breathlessness at peak exercise (8.6 [SD 2.1] vs 4.9 [3.1], p < 0.01). Although from a small sample, these findings suggest that DDD pacing with a short atrioventricular delay may have therapeutic potential in patients with dilated cardiomyopathy, even in the absence of conventional indications for pacemaker implantation.

Diastolic mitral regurgitation in patients with first-degree atrioventricular block

Diastolic mitral regurgitation has been observed in patients with DDD pacemakers when the atrioventricular (AV) delay was prolonged. However, diastolic mitral regurgitation associated with first-degree AV block has not been fully studied. We examined transmitral blood flow in 24 patients with first-degree AV block and normal cardiac function (ages 35.3 +/- 17.4 years), and in nine patients with DDD pacemakers and normal cardiac function (ages 73.1 +/- 8.1 years), using pulsed Doppler echocardiography. Diastolic mitral regurgitation was observed in 19 of 24 patients with first-degree AV block. Although PQ interval was shortened from 0.32 +/- 0.06 to 0.20 +/- 0.05 seconds (P < 0.01) after 1 mg atropine sulfate IV, the interval between P wave (ECG) and the beginning of diastolic mitral regurgitation did not change, while the duration of diastolic mitral regurgitation was shortened from 0.15 +/- 0.03 to 0.05 +/- 0.03 seconds (P < 0.01). There was a significant correlation between changes in PQ interval and changes in the duration of diastolic mitral regurgitation (r = 0.92, P < 0.001). Although cardiac output (3.9 +/- 0.05 L/min) and pulmonary capillary wedge pressure (5.1 +/- 1.5 mmHg) were normal in all patients with pacemakers, diastolic mitral regurgitation was observed when the AV delay was prolonged. The critical PQ interval for the appearance of diastolic mitral regurgitation was 0.23 +/- 0.01 seconds. In patients with prolonged PQ intervals, delayed ventricular contraction following atrial contraction may be associated with mitral regurgitation in the presence of a reversed AV pressure gradient.(ABSTRACT TRUNCATED AT 250 WORDS)

Diastolic mitral regurgitation with atrioventricular conduction abnormalities: relation of mitral flow velocity to transmitral pressure gradients in conscious dogs

Diastolic mitral regurgitation is a common finding that can be detected with use of Doppler echocardiographic techniques in patients with atrioventricular (AV) conduction abnormalities. With use of simultaneous hemodynamic and Doppler techniques, mitral flow velocity, mitral valve motion and transmitral pressure gradient were studied during 50 cardiac cycles each of spontaneous or atrial paced first- and second-degree AV block in five lightly sedated dogs. Diastolic mitral regurgitation was detected during atrial relaxation on all beats in which ventricular contraction was delayed greater than 190 ms. In all dogs the diastolic regurgitation was associated with a reverse transmitral pressure gradient (3.7 +/- 1.1 mm Hg in first-degree AV block and 3.2 +/- 1.5 mm Hg in second-degree AV block) that occurred primarily as the result of a decrease in atrial pressure with atrial relaxation. These reverse pressure gradients were as large as the maximal forward transmitral gradients in early diastole (2.9 +/- 0.9 mm Hg in first-degree AV block and 3.1 +/- 0.7 mm Hg in second-degree AV block) and larger than the maximal forward pressure gradients at atrial contraction (1.7 +/- 0.5 and 1.4 +/- 0.6 mm Hg, respectively, p less than 0.05). The maximal reverse pressure gradient during atrial relaxation was also as large as the reverse pressure gradient in mid-diastole (2.7 +/- 0.9 and 2.8 +/- 1.0 mm Hg, respectively), associated with deceleration of early diastolic mitral flow. Peak diastolic mitral regurgitation velocity coincided with the maximal reverse transmitral gradient and was usually larger than anterograde mitral flow velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

Observations on Doppler mid-diastolic mitral flow reversal

Mitral regurgitation is detected occasionally in diastole during severe aortic regurgitation, hypertrophic cardiomyopathy and atrioventricular block. We have noticed mitral mid-diastolic flow reversal in both patients and many normal subjects. To evaluate this flow phenomenon, pulsed Doppler mitral flow velocity and M-mode echocardiographic recordings were obtained in 38 normal subjects (age range, 16 to 61 years). Fifteen of 38 subjects (40%) had mid-diastolic flow reversal, defined as reversed flow occurring in mid-diastole with a duration greater than 50 msec. Mid-diastolic flow reversal was more common in subjects with longer RR intervals (1031 versus 893 msec), more rapid M-mode echocardiographic EF (early diastolic deceleration) slopes of mitral valve anterior leaflet motion (141 versus 93 mm/sec), and more rapid deceleration of early diastolic mitral flow velocities (612 versus 426 cm/sec2). Mid-diastolic flow reversal by Doppler color flow mapping was recorded in the left atrium in all subjects, even in subjects without mid-diastolic flow reversal shown by pulsed Doppler echocardiography. However, subjects with mid-diastolic flow reversal detected by pulsed Doppler echocardiography demonstrated greater extension of flow into left atrium (10.4 versus 4.1 mm) and longer duration (112 versus 69 msec) of color flow reversal. These data suggest that mid-diastolic flow reversal represents a physiologic intravalvular flow that is possibly the result of reflected flow from the vigorous early diastolic mitral semiclosure.

Diastolic mitral regurgitation in acute but not chronic aortic regurgitation: implications regarding the mechanism of mitral closure

In acute aortic regurgitation, left ventricular pressure rises rapidly during diastole, which produces presystolic mitral valve closure. This does not occur in chronic aortic regurgitation. Since normal, nonregurgitant mitral valve closure may depend on properly coordinated atrial and ventricular contractions, we hypothesized that abnormal mitral valve closure occurring before systole in acute aortic regurgitation may produce diastolic mitral regurgitation detectable by Doppler echocardiography. Accordingly, we performed ultrasonic Doppler examination of seven patients with acute aortic regurgitation and 12 patients with chronic aortic regurgitation. Regurgitant aortic flow was severe in all cases. Doppler sampling within the left atrium demonstrated regurgitant mitral flow in late diastole in all patients with acute aortic regurgitation. The onset of diastolic mitral regurgitation coincided with mitral valve preclosure in patients with acute aortic regurgitation and occurred regardless of the position of the mitral leaflets at the initiation of closure. In contrast, none of the 12 patients with chronic aortic regurgitation had mitral valve preclosure or diastolic mitral regurgitation (p less than 0.05 versus acute aortic regurgitation). We conclude that diastolic mitral regurgitation accompanies mitral valve preclosure, which occurs in acute but not chronic aortic regurgitation. Thus diastolic mitral regurgitation may be a Doppler sign of acute aortic regurgitation, in the absence of a markedly prolonged PR interval. Furthermore, this observation suggests that normal, nonregurgitant mitral closure requires more than an increase in left ventricular pressure above left atrial pressure, regardless of the position of the mitral leaflets before closure.

Diastolic atrioventricular valve closure and regurgitation following atrial contraction: their relation to timing of atrial contraction

Some authors have proposed that atrial contraction per se is able to close the atrioventricular (AV) valves. To determine whether tight closure of the AV valves can be accomplished solely by atrial contraction, the existence of diastolic regurgitation following atrial contraction and its relation to the PQ interval were examined in 13 patients with AV block (2 of the first degree, 4 of the second degree, and 7 of the third degree), using pulsed Doppler echocardiography, which allowed noninvasive estimation of valvular regurgitation in the physiological state. Diastolic mitral and tricuspid regurgitations were detected in the left and right atria near the respective AV valves in all 13 patients despite different degrees of AV block, while these valves were observed to be in apparently closed position during regurgitation on the two-dimensional and M-mode echocardiograms. The duration of regurgitant signals was prolonged with an increase in the PQ interval in the electrocardiogram, but it became short again as the P wave approached the preceding rapid filling wave. These results suggest that atrial contraction may initiate the closure of the AV valves but is not capable of closing the valves tightly, and atrial contraction with long PQ interval may contribute little to augmentation of cardiac output in patients with AV block.

Late diastolic mitral regurgitation studied by pulsed Doppler echocardiography

To evaluate the usefulness of pulsed Doppler echocardiography in assessing late diastolic mitral regurgitation (MR) and to clarify the pathophysiology of MR, 226 consecutive patients who had undergone left ventriculography were studied. By investigating blood flow patterns at the left atrial outflow tract, late diastolic disturbed flow suggesting MR was detected in 15 patients (7%), including 10 (4%) with positive left ventriculographic findings. Among these 15 patients, 14 (93%) had atrial fibrillation and had late diastolic MR in the cardiac cycle with prolonged RR interval. The limitation in number of cardiac cycles that could be analyzed and the rapid heart rate eliminating appearance of the beat with prolonged RR interval may be the reasons for the paucity of late diastolic MR by left ventriculography. Ten patients (66%) with late diastolic MR, including 1 with sinus rhythm, had aortic regurgitation, 3 had high-grade systolic MR and 2 had atrial septal defect. Simultaneous recording of pulmonary artery wedge pressure and left ventricular pressure in 3 patients showed a reversal of pressure gradient in late diastole when the RR interval was prolonged. In conclusion, pulsed Doppler echocardiography was useful for detecting late diastolic MR and in reducing overestimation of systolic MR in left ventriculography induced by erroneous addition of late diastolic MR. The difference of the incidence of this flow between left ventriculography and Doppler examination indicated that this flow depends primarily on heart rate and may come and go in a patient.

Evaluation by pulsed Doppler echocardiography of the atrial contribution to left ventricular filling in patients with DDD pacemakers

To evaluate the significance of the left atrial (LA) contribution to left ventricular (LV) filling in cardiac pacing, LV inflow velocity was recorded with pulsed Doppler echocardiography in 20 patients with a DDD pacemaker. The pacemaker was programmed to atrioventricular (AV) sequential pacing with AV intervals of 50, 100, 150, 200 and 250 ms, and then to VVI pacing at a fixed rate of 70 beats/min. To evaluate the relative changes of LV filling volume in individual patients, the percent change in time-velocity integral of LV inflow velocity in each pacing mode was calculated as the ratio to that of AV sequential pacing with an AV interval of 150 ms. To estimate the degree of LA contribution to LV filling, the ratio of time-velocity integral during LA ejection phase to that during total LV filling phase was measured at the optimal AV interval. The percent LV inflow volume in AV sequential pacing was 74% for an AV interval of 50 ms, 87% for 100 ms, 98% for 200 ms and 90% for 250 ms. The percent LV inflow volume in VVI pacing was 72%. The percent LV inflow volume at AV intervals of 150 ms was significantly greater than that at an AV interval of 50, 100 and 250 ms, and in VVI pacing (p less than 0.05). The degree of LA contribution to LV filling showed a positive correlation with the percent increase of LV inflow volume with mode conversion from VVI to AV sequential pacing (p less than 0.005) and also with age (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Diastolic mitral regurgitation in patients with atrioventricular conduction abnormalities: a common finding by Doppler echocardiography

M-mode and Doppler echocardiography were performed in 16 patients with first degree atrioventricular (AV) block, 1 patient with second degree (Wenckebach type) and 3 patients with third degree AV block; 20 individuals with a normal PR interval served as control subjects. The time from the onset of the P wave to the mitral valve closure by M-mode and to the end of mitral flow by Doppler echocardiography were obtained. In 20 normal subjects, the P wave to mitral valve closure interval measured 220 +/- 30 ms by M-mode and to the end of mitral flow 225 +/- 29 ms by Doppler technique (p = NS). In patients with first degree AV block, these intervals measured 242 +/- 41 and 249 +/- 36 ms, respectively (p = NS). Late diastolic (before the onset of the QRS complex) mitral regurgitation was detected by pulsed mode Doppler imaging in 9 (56%) of the 16 patients with first degree AV block but in none with a normal PR interval. In the four patients with advanced AV block, intermittent mid or late diastolic mitral regurgitation was found to depend on the position of the P wave in diastole. With early diastolic P waves, the end of mitral valve flow by Doppler technique occurred 230 to 250 ms after the onset of the P wave and was followed by mild diastolic mitral regurgitation of variable duration. With P waves falling in systole, the mitral valve remained open throughout diastole; during most of diastole, however, there was neither forward mitral flow (diastasis) nor diastolic mitral regurgitation detected by Doppler technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Diastolic mitral regurgitation in patients with hypertrophic cardiomyopathy

An analysis of the left ventricular angiograms of 31 patients with hypertrophic cardiomyopathy revealed diastolic mitral regurgitation in 4, a prevalence of 12.9%. The clinical, echocardiographic, angiographic, and hemodynamic data of these patients were reviewed. Diastolic mitral regurgitation could not be attributed to arrhythmia, PR interval prolongation, atrioventricular dissociation, aortic insufficiency, or aortic stenosis. Reduced left ventricular compliance was evidenced by elevated end-diastolic pressure following angiography and reduced diastolic E-F slope on echocardiography. It is speculated that the rapid inflow of blood into a poorly compliant ventricle established a turbulent flow pattern that resulted in the "floating" of blood back into the left atrium.

Kearns' syndrome, a new form of cardiomyopathy

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Diastolic mitral regurgitation. Haemodynamic and angiographic correlation

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Atriogenic mitral valve reflux: diastolic mitral incompetence following isolated atrial systoles

Cardiac and aortic pressures were recorded after stellate ganglionectomy and vagotomy. Acute heart block was produced by injecting the atrioventricular node, and atrial and ventricular systoles were controlled electronically to occur independently or in any desired relationship. Angiocardiograms recorded on video tape after injections of 4 ml 69% Renovist into the left ventricle were analyzed with a videodensitometer able to detect small refluxes of contrast medium into the left atrium and correlate them with phases of the cardiac cycle. When ventricular driving was temporarily suspended but atrial driving continued, pressure records indicated mitral valve closure after each atrial systole, but reflux of contrast medium into the atrium occurred after each systole not followed by a normally sequenced ventricular systole. Driving with a 2: 1 atrioventricular stimulation resulted in reflux, with the alternate atrial contraction dissociated from ventricular systole. Thus, the mitral valve was not effectively closed by atrial systoles that were not followed by normally sequenced ventricular systoles.