Response of the interatrial septum to transatrial pressure gradients and its potential for predicting pulmonary capillary wedge pressure: an intraoperative study using transesophageal echocardiography in patients during mechanical ventilation.

OBJECTIVES: We hypothesized that the directional movement of the interatrial septum and its curvature may reflect the pressure relations between the left and right atria. BACKGROUND: Interventricular septal shape is primarily dependent on the pressure gradient between the left and the right ventricle. No analogous study has carefully evaluated the determinants of interatrial septum shape and motion. METHODS: Patients (n = 52) undergoing cardiac or vascular surgery were studied intraoperatively at multiple intervals with transesophageal echocardiography and simultaneous measurement of central venous pressure, pulmonary capillary wedge pressure and airway pressure. RESULTS: Overall interatrial septum shape, which usually curved toward the right atrium, changed concordantly with the interatrial pressure gradient (pulmonary capillary wedge pressure-central venous pressure difference). The degree of interatrial septum curvature was also primarily dependent on the interatrial pressure gradient and, to a lesser extent, was affected by changes in left atrial size (F = 130.4 vs. F = 14.1). During passive mechanical expiration, the interatrial pressure gradient, usually positive, often reverses transiently and the interatrial septum momentarily bows toward the left atrium. Midsystolic reversal was seen in 64 of 72 episodes when the pulmonary capillary wedge pressure was < or = 15 mm Hg but in only 2 of 40 episodes when it was > 15 mm Hg (sensitivity = 0.89, specificity = 0.95, positive predictive value = 0.97). CONCLUSIONS: These findings suggest that overall interatrial septum shape depends on the pressure gradient between the left and right atria. Midsystolic reversal of the interatrial septum, which probably reflects the increased venous return in the right relative to the left atrium during mechanical expiration, may be a useful indicator of the pulmonary capillary wedge pressure.

Safety and efficacy of hydrogen peroxide plasma sterilization for repeated use of electrophysiology catheters.

OBJECTIVES: The purpose of this study was to evaluate a new technique for sterilizing nonlumen electrophysiology catheters that uses hydrogen peroxide gas plasma. BACKGROUND: The reuse of electrophysiology catheters may potentially result in a significant cost savings. While ethylene oxide sterilization appears to be safe and effective from a clinical standpoint, toxic ethylene oxide residuals, which exceed Food and Drug Administration standards, have been reported. METHODS: Ten nonlumen electrophysiology catheters were extensively evaluated. Each catheter was used five times and resterilized after each use with hydrogen peroxide gas plasma. Tests for sterility, mechanical and electrical integrity, chemical residuals and standard and electron microscopic inspection were performed. RESULTS: Loss of electrical integrity or mechanical integrity was not observed in any catheter. No evidence of microbial contamination was found. Surface integrity was preserved except for one ablation catheter that exhibited fraying of the insulation at the insulation-electrode interface. Surface inspection using standard magnification and electron microscopy revealed no significant change in surface characteristics associated with the sterilization process. Hydrogen peroxide was the only chemical residual noted, with an average concentration of 0.22% by weight, which is within accepted American Association for the Advancement of Medical Instrumentation limits. The cost for a standard electrophysiology catheter ranges from $200 to $800, and one sterilization cycle costs $10. If electrophysiology catheters are used five times, resterilization could potentially result in a savings of $2,000 per catheter, or $9,000 for five ablation procedures. CONCLUSIONS: Hydrogen peroxide gas plasma sterilization may provide a cost-effective means of sterilizing nonlumen electrophysiology catheters without the problem of potentially harmful chemical residuals. However, careful visual inspection of catheters, particularly at the insulation-electrode interface, is required if catheter reuse is performed.

The flail mitral valve: echocardiographic findings by precordial and transesophageal imaging and Doppler color flow mapping.

To determine the echocardiographic and Doppler characteristics of mitral regurgitation associated with a flail mitral valve, precordial and transesophageal echocardiography with pulsed wave and Doppler color flow mapping was performed in 17 patients with a flail mitral valve leaflet due to ruptured chordae tendineae (Group I) and 22 patients with moderate or severe mitral regurgitation due to other causes (Group II). Echocardiograms were performed before or during cardiac surgery; cardiac catheterization was also performed in 28 patients (72%). Mitral valve disease was confirmed at cardiac surgery in all patients. By echocardiography, the presence of a flail mitral valve leaflet was defined by the presence of abnormal mitral leaflet coaptation or ruptured chordae. Using these criteria, transesophageal imaging showed a trend toward greater sensitivity and specificity than precordial imaging in the diagnosis of flail mitral valve leaflet. By Doppler color flow mapping, a flail mitral valve leaflet was also characterized by an eccentric, peripheral, circular mitral regurgitant jet that closely adhered to the walls of the left atrium. The direction of flow of the eccentric jet in the left atrium distinguished a flail anterior from a flail posterior leaflet. By transesophageal echocardiography with Doppler color flow mapping, the ratio of mitral regurgitant jet arc length to radius of curvature was significantly higher in Group I than Group II patients (5.0 +/- 2.3 versus 0.7 +/- 0.6, p less than 0.001); all of the Group I patients and none of the Group II patients had a ratio greater than 2.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency catheter ablation versus medical therapy for initial treatment of supraventricular tachycardia and its impact on quality of life and healthcare costs.

We prospectively compared the impact on quality of life and cost effectiveness between ablation and medication as an initial strategy for patients with paroxysmal supraventricular tachycardia (SVT). Seventy-nine consecutive patients with newly documented paroxysmal SVT were treated with either ablation or medication. Health surveys (SF-36 and disease-specific questions) were obtained at baseline and after 12 months of follow up. Cost of health care utilization for the 6 months before and after treatment were measured. Both medication and ablation improved quality of life. However, ablation improved quality of life in more general health categories than medication. At follow up, ablation was associated with significantly improved quality of life in the bodily pain (63+/-24 vs 81+/-20, p <0.005), general health (69+/-21 vs 79+/-21, p <0.05), vitality (55+/-21 vs 66+/-22, p <0.05), and role emotion (78+/-36 vs 94+/-17, p <0.05) categories when compared with medication. Although both medication and ablation decreased frequency of disease-specific symptoms, ablation resulted in complete amelioration of symptoms in more patients (33% vs 74%). Potential long-term costs were similar for medication and ablation. In conclusion, ablation improves health-related quality of life to a greater extent, and in more aspects of general and disease-specific health than medication.

Trends and patterns in electrophysiologic and ablation catheter reuse in the United States.

In a survey of 140 electrophysiologic laboratories in the USA, 49% reuse catheters to some extent. Catheter reuse is associated with significant reductions in cost but is not conducted in a standardized fashion.

Measurement of aortic blood flow by Doppler echocardiography: temporal, technician, and reader variability in normal subjects and the application of generalizability theory in clinical research.

Although Doppler echocardiographic measurements of aortic flow have been found to correlate with stroke volume, the reliability of this technique is unknown. The purpose of this study was to measure the reliability of Doppler estimates of cardiac output by identifying and estimating the magnitude of different sources of error. We measured the reliability of Doppler estimates of cardiac output by identifying the magnitude of sources of error in 11 subjects with studies performed by two technicians and read by two readers. Analysis with generalizability theory demonstrated that the largest portion of the total variance was from differences among patients, with a smaller contribution due to day-to-day variability. Variability due to technician was low for continuous wave Doppler (2.0%), but high for pulsed wave (23.2%). Thus continuous wave, but not pulsed wave Doppler measurements, can be used to detect serial changes in cardiac output due to an intervention.

Streptococcal endocarditis temporally related to transesophageal echocardiography.

A case of streptococcal sanguis endocarditis temporally related to a transesophageal echocardiogram is reported; and the literature on the incidence of bacteremia occurring during transesophageal echocardiography is reviewed. On the basis of this case and review of the literature, a reevaluation of the current guidelines for endocarditis prophylaxis during this procedure is recommended.

Cardiac pacing in patients with dilated cardiomyopathy.

Studies of both the acute and chronic effects of permanent cardiac pacing in patients with dilated cardiomyopathy have produced contradictory results. Similarly, theoretically promising novel pacing techniques such as multisite, His bundle, and right ventricular outflow tract pacing have also yielded mixed results in preliminary studies. In general, at the present time, pacing therapy should be considered investigational for patients with dilated cardiomyopathy who do not have traditional bradycardia indications; nevertheless, pacing therapy may be useful in a small population of patients with dilated cardiomyopathy who have inappropriate timing of left ventricular and left atrial contraction. The beneficial effects of cardiac pacing in some patients with DCM cannot be dismissed out of hand; they must be explained. What is needed is clarification of the best methods to measure any benefits of this therapy: among the options are echocardiographically determined parameters of forward flow and AV valve function, exercise test parameters such as duration and O2 consumption, global and regional ejection fraction, functional classification, quality of life questionnaires, neurohumoral parameters such as plasma atrial natriuretic peptide and catecholamines, and, finally, disease progression and survival.

Effects of aging on AV nodal and ventricular beta-adrenergic receptors in the Fischer 344 rat.

The effects of aging on atrioventricular (AV) nodal and right and left ventricular beta-adrenergic receptor (beta-AR) characteristics were studied in Fischer 344 rat hearts using quantitative autoradiography. Twenty-micrometer-thick cardiac sections containing the compact AV node from 16 mature (4-6 mo old) rats, 6 middle-aged (12 mo old) rats, and 16 old (24 mo old) rats were incubated with [125I]iodocyanopindolol, [125I]iodocyanopindolol plus atenolol, or ICI 118551. Saturation experiments revealed a significant age-related decrease in AV nodal beta-AR density (mature: 190 +/- 46, middle-aged: 165 +/- 27, old: 133 +/- 34 amol/mm2; P < 0.01), with no change in affinity (mature: 106 +/- 62, middle-aged: 132 +/- 46, old: 128 +/- 66 pM). No age-related changes in AV nodal beta-AR subtype ratio (55% beta 1, 45% beta 2) or estimated compact AV node volume were detected (mature: 66 +/- 17, old: 65 +/- 23 microns 3). No difference in beta-AR density or affinity was detected between mature and old rats in either left (LV) or right (RV) ventricular tissue (LV, mature: 60 +/- 11, middle-aged: 59 +/- 11, old: 62 +/- 11 amol/mm2; RV, mature: 65 +/- 9, middle-aged: 65 +/- 11, old: 58 +/- 10 amol/mm2). beta-AR subtype ratios for the left ventricle (64% beta 1, 36% beta 2) and right ventricle (63% beta 1, 37% beta 2) did not significantly differ between mature and old rats. To summarize, aging from 4 to 24 mo in the Fischer 344 rat is associated with 1) a decrease in AV nodal beta-AR density with no change in affinity; 2) no change in volume of the compact region of the AV node; 3) no change in beta-AR subtype ratio in the AV node, left ventricle, or right ventricle; and 4) no change in either RV or LV beta-AR density.

Pulmonary venous flow patterns by transesophageal pulsed Doppler echocardiography: relation to parameters of left ventricular systolic and diastolic function.

We have previously shown that the systolic and diastolic pulmonary venous flow (PVF) distribution is predictive of left atrial pressure. This study was designed to define the confounding influences of left atrial expansion, descent of the mitral anulus, and left ventricular contractile function on that relationship; to define normal PVF patterns; and to document the interaction of PVF with mitral inflow. Therefore we studied 27 consecutive intraoperative patients with coronary artery disease (22 men and 5 women, ages 35 to 78 years) using transesophageal echocardiography. A group of 12 normal subjects served as a control. Doppler and two-dimensional echocardiographic parameters were obtained simultaneously with monitoring pulmonary capillary wedge pressure (PCWP). We found that neither left atrial expansion nor the descent of the mitral anulus influenced the relationship between PVF and PCWP, but that left ventricular fractional shortening confounded this relationship. In normal subjects PVF was dominant in systole, whereas PVF in patients with elevated PCWP was dominant in diastole (systolic fraction of 68 +/- 6% [SD] in normals versus 42 +/- 15% in patients with PCWP greater than or equal to 15 mm Hg). PVF velocities interacted with transmitral flow velocities. Peak early diastolic mitral inflow velocities increased linearly with peak early diastolic PVF velocities (r = 0.62). We conclude that systolic and diastolic PVF distribution is mainly determined by the level of PCWP and to a lesser extent by left ventricular contraction, but not by left atrial expansion or by mitral anulus descent. Transesophageal pulsed Doppler echocardiography of PVF provides useful clinical information about the level of PCWP in intraoperative patients with coronary artery disease.

Responses to calcium and binding of 3H-nimodipine in the atrioventricular node, atria, and ventricles of mature and old male Fischer 344 rats.

To determine whether aging alters cardiac calcium dose responses or dihydropyridine receptor density or affinity, we performed (a) calcium (Ca2+) dose-response studies (3-5 mM) in Langendorff perfused hearts from 12 mature (4-7 month) and 12 old (23-27 month) Fischer 344 rats, and (b) quantitative autoradiography experiments with 3H-nimodipine (50-3,000 pM) in 20-microns tissue sections containing the compact AV node from hearts of eight mature and eight old F344 rats. Baseline AA interval, AV conduction time, AV Wenckebach block cycle length, and QRS duration were prolonged in isolated hearts from old compared with mature rats. In contrast, neither left ventricular developed pressure nor peak dP/dt was altered by age. Perfusion with increasing concentrations of Ca2+ produced decreased coronary perfusion (p < 0.001) without age-related alterations in AA intervals, AV conduction times, dP/dt, or left ventricular developed pressure. No age-related differences in AV node 3H-nimodipine binding (Bmax: mature, 1.35 +/- 0.41 fmol/mm2; old, 1.33 +/- 0.43 fmol/mm2) or affinity (Kd: mature, 915 +/- 375 pM; old, 973 +/- 369 pM) were detected. Similarly, no age-related differences in 3H-nimodipine receptor number or affinity were detected in left and right ventricular or atrial tissue. Total protein in atrial and ventricular tissue was unchanged with age. However, left atrial and left ventricular isolated membrane protein was significantly lower in senescent compared with mature rat hearts (left ventricle: mature, 49.4 +/- 8.7 mg/g; old, 40.9 +/- 3.5 mg/g; p < 0.05; left atria: mature, 36 +/- 9 mg/g; old, 28 +/- 3 mg/g; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A left free-wall, decrementally conducting, atrioventricular (Mahaim) fiber: diagnosis at electrophysiological study and radiofrequency catheter ablation guided by direct recording of a Mahaim potential.

A 64-year-old female with Wolff-Parkinson-White syndrome and an ECG demonstrating a right posterolateral accessory pathway was referred for electrophysiological study. During electrophysiological testing two AV pathways were identified: a right posterolateral pathway that displayed conventional electrophysiological properties: and a left free-wall pathway that conducted only anterogradely and demonstrated decremental properties. Two separate wide complex tachycardias were induced that utilized the left free-wall pathway anterogradely and either the AV node or the right posterolateral accessory pathway retrogradely. A discrete electrical potential on the free wall of the mitral annulus was identified during tachycardia and was utilized to facilitate mapping and ablation.

Extensive trans-species mitochondrial polymorphisms in the carabid beetles Carabus subgenus Ohomopterus caused by repeated introgressive hybridization.

To study the potential importance of introgressive hybridization to the evolutionary diversification of a carabid beetle lineage, we studied intraspecific and trans-species polymorphisms in the mitochondrial NADH dehydrogenase subunit 5 (ND5) gene sequence (1083 bp) in four species of the subgenus Ohomopterus (genus Carabus) in central and eastern Honshu, Japan. Of the four species, C. insulicola is parapatric with the other three, and can hybridize naturally with at least two. This species possesses two haplotypes of remote lineages. We classified ND5 haplotypes using polymerase chain reaction-restriction fragment length polymorphism with TaqI endonuclease for 524 specimens, and sequenced 143 samples. Analysis revealed that each species was polyphyletic in its mitochondrial DNA phylogeny, representing a marked case of trans-species polymorphism. Recent one-way introgression of mitochondria from C. arrowianus nakamurai to C. insulicola, and from C. insulicola to C. esakii, was inferred from the frequency of identical sequences between these species and from direct evidence of hybridization in their contact zones. Other intraspecific polymorphisms in the four species may be due to undetected introgressive hybridization (e.g. C. insulicola to C. maiyasanus) or from stochastic lineage sorting of ancestral polymorphisms. This beetle group has a genital lock-and-key system, with species-specific or subspecies-specific genital morphology that may act as a barrier to hybridization. However, our results demonstrate that introgressive hybridization has occurred multiple times, at least for mitochondria, despite differences among, and stability within, morphological characters that distinguish local populations. Thus, hybridization and introgression could have been key processes in the evolutionary diversification of Ohomopterus.

Estimation of mean left atrial pressure from transesophageal pulsed Doppler echocardiography of pulmonary venous flow.

To determine whether pulmonary venous flow and mitral inflow measured by transesophageal pulsed Doppler echocardiography can be used to estimate mean left atrial pressure (LAP), we prospectively studied 47 consecutive patients undergoing cardiovascular surgery. We correlated Doppler variables of pulmonary venous flow and mitral inflow with simultaneously obtained mean LAP and changes in pressure measured by left atrial or pulmonary artery catheters. Among the pulmonary venous flow variables, the systolic fraction (i.e., the systolic velocity-time integral expressed as a fraction of the sum of systolic and early diastolic velocity-time integrals) correlated most strongly with mean LAP (r = -0.88). Of the mitral inflow variables, the ratio of peak early diastolic to peak late diastolic mitral flow velocity correlated most strongly with mean LAP (r = 0.43), but this correlation was not as strong as that with the systolic fraction of pulmonary venous flow. Similarly, changes in the systolic fraction correlated more strongly with changes in mean LAP (r = -0.78) than did changes in the ratio of peak early diastolic to peak late diastolic mitral inflow velocity (r = 0.68). We conclude that in the surgical setting observed, pulmonary venous flow from transesophageal pulsed Doppler echocardiography can be used to estimate mean LAP. This technique may provide a rapid, simple, and relatively noninvasive means of gauging this variable in patients undergoing intraoperative transesophageal echocardiography.