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Long-term cardiac allograft valves after heart transplant are functionally and structurally preserved, in contrast to homografts and bioprostheses.

BACKGROUND AND AIM OF THE STUDY: Homograft valves undergo degenerative changes over time, which finally lead to functional deterioration. Immunological events are believed to play a pivotal role in this process. To further evaluate this hypothesis, the valvular morphology and function, as well as comorbidities predisposing to deteriorative processes, were evaluated in patients who had undergone heart transplant more than 10 years previously. METHODS: In a consecutive cohort of 146 patients (125 males, 21 females; mean age at transplant 43.8 +/- 11.2 years), heart and valve function were assessed by color Doppler echocardiography at a mean of 5306 +/- 987 days after heart transplant. Evaluated parameters included chamber dimensions, cardiac function, valvular morphology/function, and concomitant diseases. RESULTS: Atrial and ventricular dimensions were within normal ranges for the left atrium (LA; n=7), right atrium (RA; n=7), left ventricle (LV; n=143) and right ventricle (RV; n=119). Slight enlargements occurred in the LA (n=138), RA (n=137), LV (n=1) and RV (n=11), while significant enlargements were seen in the LA (n=1), RA (n=2), LV (n=2), and RV (n=16). With regard to cardiac function, the ejection fraction (EF) was 63.9 +/- 4.9%, left ventricular isovolumic relaxation time (IVRT) 85.04 +/- 14.64 ms, fractional shortening (FS) 34 +/- 12%, and pulmonary artery systolic pressure (PASP) 29.81 +/- 6.4 mmHg. Valvular regurgitation (grade > or =2) was present in 34 patients (31 tricuspid valves, three mitral valves). No patients presented with aortic valve regurgitation. Concomitant conditions with a potential impact on calcium balance/valvular deterioration included immunologic/chronic inflammatory diseases (n=6), malignancies (n=12), kidney (n=41), cardiovascular system (n=39) and thyroid/parathyroid (n=12). CONCLUSION: During the long term after heart transplant, heart valves were characterized by normal morphology and function in the majority of cases. Although most patients presented with concomitant conditions strongly predisposing for valvular deterioration/calcification, sole immunosuppressive/anti-inflammatory therapy appears to prevent these processes in heart transplant patients.

Adult↗

5-Hydroxytryptamine causes rate-dependent arrhythmias through 5-HT4 receptors in human atrium: facilitation by chronic beta-adrenoceptor blockade.

We have investigated the ability of 5-hydroxytryptamine (5-HT) to elicit arrhythmic contractions in isolated human atrial strips as a function of pacing rate (0.1-2 Hz) using a method recently introduced by us (Kaumann and Sanders, this journal, 1993 b) and examined the nature of the 5-HT receptors involved. Right atrial appendage tissue was obtained from 14 patients undergoing cardiac surgery. None of the patients had advanced heart failure. 5-HT (0.6-20 mumol/l) induced arrhythmic contractions during pacing in 4/11 atrial strips from 3/4 patients who had not received beta blockers and in 21/27 atrial strips from 9/10 patients who had been chronically treated with beta blockers (primarily beta 1-selective). The incidence of arrhythmic contractions evoked by 5-HT did not reach statistical significance in the atrial tissue from the non-beta blocked patients but was highly significant in the atrial tissue from the chronically beta blocked patients. The arrhythmic contractions usually occurred more frequently at low than at high pacing rates and were observed at the physiological frequency of 1 Hz in 1/4 atrial strips from 1/4 of the non-beta blocked patients and 6/11 strips from 5/10 of the beta blocked patients. The 5-HT-evoked arrhythmic contractions were observed during blockade of beta 1-adrenoceptors, beta 2-adrenoceptors and 5-HT3 receptors, ruling out the participation of these receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗

Systolic improvement and mechanical resynchronization does not require electrical synchrony in the dilated failing heart with left bundle-branch block.

BACKGROUND: Biventricular (BiV) and left ventricular (LV) pacing similarly augment systolic function in left bundle-branch block (LBBB)-failing hearts despite different electrical activation. We tested whether electrical synchrony is required to achieve mechanical synchronization and functional benefit from pacing. METHODS AND RESULTS: Epicardial mapping, tagged MRI, and hemodynamics were obtained in dogs with LBBB-failing hearts during right atrial, LV, and BiV stimulation. BiV and LV both significantly improved chamber hemodynamics (eg, 25% increase in dP/dt(max) and aortic pulse pressure) compared with atrial pacing-LBBB, and this improvement correlated with mechanical resynchronization. Electrical dispersion, however, decreased 13% with BiV but increased 23% with LV pacing (P<0.01). CONCLUSION: Improved mechanical synchrony and function do not require electrical synchrony. Mechanical coordination plays the dominant role in global systolic improvement with either pacing approach.

Animals↗

Late-diastolic forward flow in the aorta induced by left atrial contraction.

Late-diastolic forward flow is a well-described phenomenon detectable by Doppler echocardiography in the pulmonary trunk. It is supported by a restrictive right ventricular diastolic function and by a low end-diastolic pulmonary artery pressure. A similar phenomenon for the left ventricle and the aorta has not been described. We report a case of a preterm infant with aortic stenosis and endocardial fibroelastosis, who underwent balloon valvuloplasty. Restrictive left ventricular diastolic filling led to high left atrial pressure (27 mm Hg) and a very pathologic ratio of early-to-late peak velocities (2.6) for an infant of 29 weeks' gestation. In combination with a low diastolic aortic pressure (24 mm Hg) caused by moderate aortic regurgitation after intervention, a late-diastolic forward flow was detectable in the aorta during left atrial contraction with pulsed Doppler echocardiography.

Aorta↗

Haemodynamic evaluation of pulmonary hypertension.

Pulmonary hypertension is characterised by the chronic elevation of pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) leading to right ventricular enlargement and hypertrophy. Pulmonary hypertension may result from respiratory and cardiac diseases, the most severe forms occurring in thromboembolic and primary pulmonary hypertension. Pulmonary hypertension is most often defined as a mean PAP >25 mmHg at rest or >30 mmHg during exercise, the pressure being measured invasively with a pulmonary artery catheter. Doppler echocardiography allows serial, noninvasive follow-up of PAPs and right heart function. When the adaptive mechanisms of right ventricular dilatation and hypertrophy cannot compensate for the haemodynamic burden, right heart failure occurs and is associated with poor prognosis. The haemodynamic profile is the major determinant of prognosis. In both primary and secondary pulmonary hypertension, special attention must be paid to the assessment of pulmonary vascular resistance index (PVRI), right heart function and pulmonary vasodilatory reserve. Recent studies have stressed the prognostic values of exercise capacity (6-min walk test), right atrial pressure, stroke index and vasodilator challenge responses, as well as an interest in new imaging techniques and natriuretic peptide determinations. Overall, careful haemodynamic evaluation may optimise new diagnostic and therapeutic strategies in pulmonary hypertension.

Blood Pressure↗

Noninvasive right and left heart catheterization: taking the echo lab beyond an image-only laboratory.

The assessment of cardiovascular hemodynamics is an extremely important component of managing patients with cardiac diseases. For years, this has been accomplished primarily through the use of right and left heart catheters placed within the cardiac chambers. Since this is an invasive technique, it should only be used when necessary; patient discomfort, infections, and overall risks for physicians would be reduced if noninvasive methods were utilized when available. Echocardiography (echo) provides the greatest ability to determine cardiovascular hemodynamics noninvasively, but requires the utmost precision and care to avoid misinterpretation. When used correctly, echocardiographic modalities provide an even greater assessment of the cardiac patient than invasive techniques. A safer and more comprehensive interpretation is available, and thus, echo should be considered the modality of choice-the new gold standard.

Atrial Function↗

[Initial experience with the use of Levovist in adult patients with suboptimal echocardiograms].

OBJECTIVE: To report our experience with the use of Levovist in echocardiographic studies. METHOD: We studied consecutively patients with suboptimal echocardiographic studies. A bolus of 4 gr @ 400 mg/ml was administered via antecubital vein and a second echocardiogram was performed during the ensuing minutes. RESULTS: Between June and July 1998 we studied 16 patients with suboptimal echocardiograms, seven males and nine females, ages 29-77. There were six patients with coronary artery disease (CAD), three with mitral regurgitation (MR), one with dynamic subaortic stenosis, five with right chambers dilatation and one with a left atrial tumor. No patient referred discomfort or had any complication-with Levovist. The mean time of the contrast effect was nine minutes. A better delineation of endocardial borders was observed this allowed better evaluation of wall motion and left ventricular function in patients with CAD. There was Doppler enhancement in patients with MR and subaortic stenosis facilitating its evaluation. We documented atrial septal defect non visualized previously in two of five patients with right chambers dilatation. There was a better delineation of the left atrial tumor. CONCLUSIONS: Levovist showed enhancement of all Doppler modalities and facilitated de evaluation of MR, left ventricular function, subaortic stenosis and a cardiac tumor. It was safe and well tolerated.

Adult↗

Hemodynamic effects of a new calcium antagonist, SR 33557, in patients with coronary artery disease and normal left ventricular function.

SR 33557 is a new calcium antagonist which in vitro demonstrated selectivity for smooth muscle over cardiac muscle. To assess the hemodynamic effects of SR 33557 in humans, SR 33557 was administered intravenously (i.v.) in 9 patients with normal systolic left ventricular function [LV ejection fraction (EF) = 63.7 +/- 8%] undergoing right and left catheterization. Baseline measurements were recorded before and during right atrial pacing (100 beats/min), after which 5 mg SR 33557 was infused in 10 min and hemodynamic parameters were continuously recorded until 30 min after discontinuation of the infusion. Effects of SR 33557 were evident from discontinuation of the infusion, maximal between the tenth and twentieth min after discontinuation of the infusion. Without atrial pacing, the main effect of SR 33557 infusion was to decrease heart rate (HR) from 77.7 +/- 10.7 to 61.9 +/- 9.3 beats/min (p < 0.001). Cardiac index (CI) did not change; stroke volume index (SVI) increased from 44.2 +/- 13 to 50.4 +/- 15 ml.m-2, (p < 0.05). Mean arterial pressure (MAP) decreased from 104.7 +/- 29.6 to 94.3 +/- 22.9 mm Hg (p < 0.05) with no change in filling pressures or systemic vascular resistance (SVR). Consequently, rate-pressure product (RPP) decreased from 8,211 +/- 3,092 to 5,906 +/- 2,025 mm Hg.beat-1 (p < 0.01). Peak positive LVdP/dt decreased from 1,711 +/- 257 to 1,533 +/- 194 (p < 0.01). During the pacing phase, none of the hemodynamic parameters differed from baseline; especially peak positive LVdP/dt remained unchanged. SR 33557 has negative chronotropic action but shows no direct negative inotropic effect in patients with normal systolic LV function.

Aged↗

A method for localizing atrial type B receptors in the dog.

1. The effect of ectopic stimulation of atria (premature ventricular contraction) on the activity of atrial type B receptors has been studied in dogs. 2. In sixteen open-chest dogs, discharge from right or left atrial type B receptors (identified by their response to pulmonary artery occlusion) was recorded. Direct stimulation of either atrium produced an increase in the activity of the left atrial but a decrease in the right atrial receptors. The earlier during the ventricular systole that the premature ventricular contraction occurred the more marked was the effect. 3. In a separate series of fourteen closed-chest experiments the right atrium was stimulated internally via the external jugular vein. The effects on the activity of the atrial type B receptors were similar to those observed during the open-chest experiments. 4. It is concluded that in the dog the technique of internal stimulation of the right atrium without opening the chest can be used to distinguish between the right and left atrial type B receptors.

Animals↗

Tetramethylammonium is a muscarinic agonist in rat heart.

Studies were designed to determine if tetramethylammonium (TMA), a quaternary amine that structurally resembles the cationic portion of acetylcholine, can affect cardiac function by acting on muscarinic receptors. Experiments examined effects of this cation on 1) the spontaneous beating rate of right atrial preparations isolated from rats, 2) force of contraction in isoproterenol-treated (0.1 microM) rat papillary muscle, and 3) quinuclidinyl benzilate ([3H]QNB) binding to rat ventricular membranes. TMA elicited concentration-dependent (0.5-50 mM) negative chronotropic and negative inotropic actions that were antagonized by the muscarinic receptor antagonist atropine. Radioligand studies showed that TMA acts as both a competitive and noncompetitive antagonist of [3H]QNB binding; the apparent dissociation constant for [3H]QNB was increased (0.092 +/- 0.025 nM in the absence of TMA; 1.14 +/- 0.204 nM in the presence of 50 mM TMA), whereas binding site density was decreased (148 +/- 26 and 65 +/- 4 fmol/mg in the absence and presence of 50 mM TMA, respectively). These results suggest that extracellular TMA can alter the function of rat heart by stimulating muscarinic receptors. This action should be considered when using this quaternary amine as a cation substitute.

Animals↗

Coexistence of sick sinus rhythm and atrial flutter-fibrillation.

A 58-year-old man with hypertensive cardiovascular disease and atrial flutter underwent electrophysiologic studies, including multiple intra-atrial recordings and atrial stimulation. Although the surface ECG suggested the presence of atrial flutter, intra-atrial recordings demonstrated the presence of (1) sinus-like rhythm localized to an area of approximately 5 mm in and around the region of the sinus node, which was protected by entrance block; (2) flutter and/or fibrillation of the remaining parts of the right atrium; (3) fibrillation of the left atrium; and (4) transient degeneration of flutter into fibrillation at right atrial sites, with predominant flutter activity. Although a major part of the right atrium was in flutter and/or fibrillation, we could assess sinus node function by overdrive stimulation of the area of sinus node-activity. Sinus node function studied revealed an underlying sick sinus syndrome.

Atrial Fibrillation↗

Right ventricular diastolic function in chronic obstructive lung disease.

Early detection of diastolic dysfunction in chronic obstructive lung disease (COLD) patients could have great prognostic value. Echocardiography has been shown to be a useful technique in studying left ventricular diastolic function. A noninvasive method of studying right ventricular diastolic function has not yet been reported. Pulsed Doppler echocardiography was used to assess right ventricular diastolic function in three groups of subjects: Group I: 35 COLD patients with pulmonary hypertension; Group II: 32 COLD patients without pulmonary hypertension; and Group III: 18 control subjects. Ratios between peak atrial filling velocity (A) and peak early filling velocity (E) (A/E), deceleration half times of the right ventricular rapid filling wave (DHT), and the interval between pulmonary valve closure and tricuspid valve opening (isovolumic relaxation times) (Pc-To) were significantly different in Group I in comparison to Groups II and III. Sensitivity of A/E ratio and Pc-To were 82 and 77%, respectively, and specificity 90 and 72%, respectively; positive predictive values were 90 and 75%, respectively, and negative predictive value 82 and 74% respectively. The multiple correlation coefficient between A/E, acceleration time (ACT), DHT, Pc-To and mean pulmonary artery pressure was 0.75 for Groups I and II together. In conclusion 2D echo-Doppler proved to be useful in evaluating right ventricular diastolic function in all hypertensive COLD patients, revealing a high correlation between diastolic parameters and mean pulmonary artery pressure in both normotensive and hypertensive COLD patients.

Echocardiography, Doppler↗

Impact of right ventricular size on ECG after percutaneous closure of atrial septal defect with Amplatzer Septal Occluder.

OBJECTIVES: To assess ECG changes after percutaneous atrial septal defect (ASD) closure in children with significant left-to-right shunt. METHODS: Analysis of data of 36 consecutive children with an ASD who had successful percutaneous ASD closure with an Amplatzer Septal Occluder. Assessment comprised echocardiography and ECG the day before and after the procedure and at 1, 6 and 12 months follow-up. RESULTS: The median age (interquartile range) of children was 7.3 (5.3) years. On the day after the procedure the end diastolic diameter of the right ventricle showed already a diminution (34 (12) mm/m2 before intervention vs. 32 (12) mm/m2). ECG changes were first observed at 1 month follow-up (PR interval before intervention 139 (20) ms vs. 132 (20) ms; QRS duration 88 (18) ms vs. 82 (19) ms) and at 6 months follow-up (QRS axis 77 degrees (33) before intervention vs. 72 degrees (53)). With the exception of the QRS duration, ECG intervals and axis were in a normal range in all patients before the procedure. Median QRS duration normalised at 1 year follow-up (83 (8) ms). CONCLUSION: After transcatheter ASD closure, decrease in right ventricular size began rapidly and was followed by reduction of the QRS duration and PR interval within weeks. Shifting to the left of the QRS axis was observed within 6 months follow-up. This study showed that ECG changes due to right ventricular volume overload can regress and normalise after percutaneous ASD closure in children.

Adolescent↗

Influence of increased abdominal pressure on steady-state cardiac performance.

The effect of steady-state increases in abdominal pressure (Pab) on cardiac performance was studied in seven acutely instrumented swine with pneumoperitoneum (PP). The animal was placed on volume-preset ventilation, and PP was created by air insufflation. Cardiac output (CO), right atrial (Pra), left atrial (Pla), pericardial (Ppe), and abdominal inferior vena cava pressures (Pivc) were measured while Pab was increased from baseline to 7.5, 15, and 30 mmHg (PP7.5, PP15, and PP30, respectively). Cardiac function curves of the right and left ventricle (RV and LV, respectively) were compared between baseline and PP30. CO presented biphasic changes, with an inital slight increase at PP7.5 followed by a fall at PP30. A significant discrepancy was observed between Pra and Pivc at PP15 and PP30, consistent with development of a "vascular waterfall." Transmural Pla (Pla - Ppe) showed parallel changes with CO, whereas transmural Pra (Pra - Ppe) exhibited a sustained increase. The RV cardiac-function curve was more depressed than was that of the LV at PP30; this suggests an increased RV afterload produced by the elevated airway pressure. These results support the hypothesis that our previously proposed concept of abdominal vascular zone conditions (M. Takata, R. A. Wise, and J. L. Robotham. J. Appl. Physiol. 69: 1961-1972, 1990) is also applicable to steady-state hemodynamic analyses. The abdominal zones appear to play an important role in determining CO, with increases in Pab, by modulating systemic venous return and the LV preload. Simultaneous measurements of Pra and Pivc may provide useful information in the hemodynamic care of patients with elevated Pab.

Abdomen↗

Atrial natriuretic peptide response to rapid atrial pacing in cardiac-denervated dogs.

The effects of rapid atrial pacing on central hemodynamics, plasma hormones, and renal function were investigated in eight control and nine cardiac-denervated dogs under chloralose anesthesia. Pacing at approximately 250 ppm for 60 min caused similar increases in pulmonary wedge and right atrial pressures, systemic vascular resistance, and plasma atrial natriuretic peptide (ANP) in both groups. In control dogs, pacing produced a fall in both plasma vasopressin (AVP) and plasma renin activity (PRA) and a rise in urine flow rate associated with an increase in free water but not sodium clearance. In contrast, in cardiac-denervated dogs, both plasma AVP and PRA increased during pacing; urine flow rate did not change, and marked sodium retention occurred. This study supports the concept that the increase in urine flow during rapid atrial pacing is mediated by inhibition of renin and AVP secretion through intact cardiac nerves. The secretion of ANP is unaffected by cardiac denervation. The natriuretic and vasodilator actions of high plasma ANP concentrations during rapid atrial pacing can be inhibited either by neurally mediated cardiorenal effects in normal animals or by stimulation of the renin-angiotensin system after cardiac denervation.

Animals↗

Right atrial versus aortic root perfusion with blood cardioplegia.

The efficacy of coronary sinus cardioplegia administered into the right atrium has not been fully defined. Thirty-two consecutive patients undergoing elective myocardial revascularization were prospectively assigned to receive cold blood cardioplegia exclusively into the aortic root (15 patients) or the right atrium (17 patients). The two groups were similar with respect to age, ventricular function, severity of coronary disease, cross-clamp time, and mean infusate volume and temperature. Completeness of revascularization was greater in the aortic root cardioplegia group (p less than 0.007). The mean septal temperature and time to achieve electromechanical arrest was greater in the right atrial cardioplegia group (p less than 0.05). The right ventricular temperature and the release of myocardial isoenzyme were similar in both groups. Left and right ventricular stroke work index was preserved equally in both cohorts. Volume loading studies performed immediately after termination of bypass suggested better left ventricular function in the aortic root cardioplegia group. Myocardial performance with a loading challenge assessed late postoperatively was superior in the right atrial cardioplegia group (p less than 0.05). There were no differences between the groups with respect to clinical outcome. The data suggest that right atrial cardioplegia (1) possesses clinical safety equal to aortic root cardioplegia, (2) possesses inferior ventricular septal cooling, and (3) yields adequate preservation of both the right and left ventricles. We conclude that right atrial cardioplegia possesses no apparent advantage over aortic root delivery in the setting of elective myocardial revascularization.

Aged↗