Novel parameters of global and regional mitral annulus geometry in man: comparison between normals and organic mitral regurgitation, before and after mitral valve repair.

AIMS: The mitral annulus (MA) saddle shape is complex but vital for a normal functioning mitral apparatus. Although conventional parameters of MA geometry such as area and height are helpful, they fall short of describing its complex regional geometry. METHODS AND RESULTS: In this prospective study, novel parameters of MA curvature and torsion were derived from three-dimensional (3D) transoesophageal echocardiography. These quantitative indices were computed in 15 patients with normal valves (age 53 ± 8 years) and in 15 patients with organic significant mitral regurgitation (MR, age 66 ± 11 years), before and after mitral valve repair (MVR). The MA was traced and modelled in mid- and end-systole. Curvature and torsion were computed at 500 points across the MA to derive regional and global indices. Overall, patients with organic MR presented the smallest global curvature and torsion; this decrease in curvature and torsion reflects a loss of tonicity of the MA tissue. These changes were largely corrected with MVR surgery, to higher values, compared with normals. The regional analysis revealed similar trends. The maximal MA curvature was found to be at the MA 'anterior horn', whereas the MA 'posterior horn' had the lowest curvature values. CONCLUSION: Novel MA parameters of curvature and torsion can be computed from 3D echocardiography and provide quantitative characteristics of dynamic regional MA geometry. In patients with organic MR, the reduced regional and global curvatures improve following surgical MVR. These quantitative parameters may help further refine the quantitative description of MA geometry in various mitral valve pathologies and after MVR.

Quantitative data analysis methods for bead-based DNA hybridization assays using generic flow cytometry platforms.

Bead-based assays are in demand for rapid genomic and proteomic assays for both research and clinical purposes. Standard quantitative procedures addressing raw data quality and analysis are required to ensure the data are consistent and reproducible across laboratories independent of flow platform. Quantitative procedures have been introduced spanning raw histogram analysis through to absolute target quantitation. These included models developed to estimate the absolute number of sample molecules bound per bead (Langmuir isotherm), relative quantitative comparisons (two-sided t-tests), and statistical analyses investigating the quality of raw fluorescence data. The absolute target quantitation method revealed a concentration range (below probe saturation) of Cy5-labeled synthetic cytokeratin 19 (K19) RNA of c.a. 1 x 10(4) to 500 x 10(4) molecules/bead, with a binding constant of c.a. 1.6 nM. Raw hybridization frequency histograms were observed to be highly reproducible across 10 triplex assay replicates and only three assay replicates were required to distinguish overlapping peaks representing small sequence mismatches. This study provides a quantitative scheme for determining the absolute target concentration in nucleic acid hybridization reactions and the equilibrium binding constants for individual probe/target pairs. It is envisaged that such studies will form the basis of standard analytical procedures for bead-based cytometry assays to ensure reproducibility in inter- and intra-platform comparisons of data between laboratories.

Emulsion strategies in the microencapsulation of cells: pathways to thin coherent membranes.

Microencapsulation of cell spheroids in an immunoselective, highly biocompatible, biomembrane offers a way to create viable implantation options in the treatment of insulin-dependent diabetes mellitus (IDDM). Traditionally the encapsulation process has been achieved through the injection/extrusion of alginate/cell mixtures into a calcium chloride solution to produce calcium alginate capsules around the cells. A novel alternative is explored here through a procedure using an emulsion process to produce thin adherent calcium alginate membranes around cell spheroids. In this study, a thorough investigation has been used to establish the emulsion process parameters that are critical to the formation of a coherent alginate coat both on a model spheroid system and subsequently on cell spheroids. Optical and fluorescence microscopy are used to assess the morphology and coherence of the calcium alginate/poly-L-ornithine/alginate (APA) capsules produced.

Quantification in situ of crystalline cholesterol and calcium phosphate hydroxyapatite in human atherosclerotic plaques by solid-state magic angle spinning NMR.

Because of renewed interest in the progression, stabilization, and regression of atherosclerotic plaques, it has become important to develop methods for characterizing structural features of plaques in situ and noninvasively. We present a nondestructive method for ex vivo quantification of 2 solid-phase components of plaques: crystalline cholesterol and calcium phosphate salts. Magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of human carotid endarterectomy plaques revealed (13)C resonances of crystalline cholesterol monohydrate and a (31)P resonance of calcium phosphate hydroxyapatite (CPH). The spectra were obtained under conditions in which there was little or no interference from other chemical components and were suitable for quantification in situ of the crystalline cholesterol and CPH. Carotid atherosclerotic plaques showed a wide variation in their crystalline cholesterol content. The calculated molar ratio of liquid-crystalline cholesterol to phospholipid ranged from 1.1 to 1.7, demonstrating different capabilities of the phospholipids to reduce crystallization of cholesterol. The spectral properties of the phosphate groups in CPH in carotid plaques were identical to those of CPH in bone. (31)P MAS NMR is a simple, rapid method for quantification of calcium phosphate salts in tissue without extraction and time-consuming chemical analysis. Crystalline phases in intact atherosclerotic plaques (ex vivo) can be quantified accurately by solid-state (13)C and (31)P MAS NMR spectroscopy.

Mitral valve repair: the multimodal approach and the role of minimally invasive procedures.

In recent years mitral valve repair has gained increasing acceptance as the preferred treatment for mitral insufficiency. Mitral valve repair has many advantages. The surgical risk is lower than prosthetic valve replacement. Improved preservation of left ventricular function due to maintenance of the papillary muscle - mitral annular continuity - has been demonstrated. Thromboembolism is rare after mitral repair in patients in sinus rhythm. These patients receive no coumadin and thus are free from bleeding complications. The repaired valves have been shown to have durability comparable to or better than prosthetic valves.

Can retrograde cardioplegia alone provide adequate protection for cardiac valve surgery?

BACKGROUND: When aortic insufficiency is present, antegrade delivery of cardioplegia requires coronary cannulation. Use of retrograde cardioplegia simplifies administration. The efficacy of the retrograde route alone in ensuring adequate myocardial protection may be assessed by the clinical outcome. METHODS AND RESULTS: We used closed transatrial coronary sinus perfusion as the sole method of cardioplegia delivery in 100 patients who underwent valve operations, either isolated or combined with coronary (n=24), ascending aortic aneurysm (n=8), or other procedures. Eighty-one patients were in New York Heart Association (NYHA) Class III or IV; 23 had undergone previous heart operations; 23 were admitted from the coronary care unit (CCU); and 20 had left ventricular ejection fraction (LVEF) of < or = 40%. Operative mortality was 2%. An intra-aortic balloon pump was required in eight patients. On univariate analysis, perioperative use of inotropes (n=26) was related to age > or = 70 years (p=0.02), COPD (p=0.05), pulmonary hypertension (p=0.005), higher NYHA Class (p=0.0006), preoperative heart failure (p=0.006), lower LVEF (p=0.0003), urgency (p=0.00001), admission from the CCU (p=0.006), repeat operation (p=0.03), coronary artery disease (p=0.02), and longer ischemic (p=0.02) and bypass times (p=0.0003). On multivariate stepwise logistic regression analysis, use of inotropes was related to preoperative lower LVEF (p=0.02) and urgency of operation (p=0.0002). Perioperative complications included ventricular arrhythmia in six, heart block in one, renal dysfunction in nine, and stroke in two patients; no patient had myocardial infarction. CONCLUSION: Good clinical results can be obtained by using retrograde cardioplegia alone without prior doses of antegrade cardioplegia in all valve operations.

Structural requirements for the cytotoxicity of the N-terminal region of HIV type 1 Nef.

We have found that the hemolytic and cytotoxic activities of myristoylated Nef N-terminal peptides require a net positive charge in the first seven amino residues of the sequence. The activities are considerably less dependent on the secondary structure of the peptides. Film balance studies showed that both active and inactive peptides interacted with neutral phospholipid monolayers, suggesting that binding to neutral lipids was not a sufficient condition for lytic activity. It was also found that nonmyristoylated N-terminal peptide did not interact to the same extent with the monolayer, indicating that myristoylation was essential for lipid interaction. It is considered that the positively charged residues of the proximate N terminus of Nef interact with acidic lipids of biological membranes, reinforcing the weak membrane-targeting properties of the myristyl chain. Parallels are drawn between this mode of interaction with membranes and that of members of the Src family of proteins, which are also myristoylated and have positively charged residues in their proximate N termini. In particular, these proteins and Nef also have serine residues in their proximal N-terminal regions, which when phosphorylated could neutralize the positive charge and thus provide a mechanism for modulating membrane interaction.

Mitral valve repair vs replacement. Current recommendations and long-term results.

Techniques now exist to correct abnormalities of all components of the mitral valvular apparatus except extensive loss of pliable leaflet area. Thus, paradoxically, myxomatous valves with redundant leaflets represent the ideal candidates for mitral valve repair. Repair for mitral insufficiency can be performed for some rheumatic valves, but patient selection is critical. Loss of leaflet area, leaflet thickening, and extensive calcification of the leaflets or commissures are contraindications to repair. The abnormalities of the subvalvular apparatus are less important because a complete set of new chordae can be reconstructed using PTFE suture material. Some cases of endocarditis are ideal for repair using localized débridement and pericardial patch repair with or without PTFE chordal replacement. True ischemic mitral regurgitation of the Carpentier type I category is still something of a surgical enigma. Because it is a restrictive leaflet motion problem, annuloplasty alone is not always effective, and the outcome of any given repair attempt is less predictable. Repairs in patients with small annuli and multiple leaflet defects requiring complex series of maneuvers have a low probability of success. Furthermore, such patients with small left ventricular cavities are more prone to experience SAM. Several factors contributing to which therapy is chosen for mitral valve disease are summarized in Table 1. Patient selection, accurate evaluation of the cause or causes of mitral regurgitation, and well-executed application of the appropriate techniques for repair are all critical factors in the early and late success of mitral valve repair.

Identification of different lipid phases and calcium phosphate deposits in human carotid artery plaques by MAS NMR spectroscopy.

Accumulation of lipids in atherosclerotic plaques causes progressive narrowing of the arterial lumen, often followed by thrombosis and ischemia. Currently several different methods, most requiring disruption of the plaque, are used to study the physical properties of lipids accumulated in plaques, and lipid composition is typically determined by chemical analysis of completely disrupted plaques. In this study, 13C magic angle spinning NMR spectroscopy (MAS NMR) was used to determine in situ the lipid composition and molecular organization of all lipid phases in human carotid artery plaques (ex vivo). Protocols were developed to observe signals from one lipid phase without interference from other phases. In addition, 31P MAS NMR detected calcification in plaques by the signals from inorganic phosphate complexed to calcium. Together, 13C and 31P MAS NMR comprise a powerful nondisruptive approach for determining the quantity and phase state of components in arterial plaques.

Assessment of myocardial viability with 99mTc-sestamibi tomography before coronary bypass graft surgery: correlation with histopathology and postoperative improvement in cardiac function.

BACKGROUND: Assessment of myocardial viability by 99mTc-sestamibi remains controversial. Accordingly, we investigated the use of sestamibi as a marker of myocardial viability, defined by histopathology, and for predicting improvement of myocardial function after coronary artery bypass graft surgery (CABG). METHODS AND RESULTS: 99mTc-sestamibi perfusion tomography and radionuclide angiography were performed within 2 days before CABG in 21 patients with > or = 75% stenosis of the left anterior descending coronary artery and resting anterior wall dyssynergy. During CABG, transmural myocardial biopsies were obtained from the dyssynergic anterior wall and from normal myocardial segments to determine the extent of viable myocardium by histopathology. Improvement of regional left ventricular function was evaluated by radionuclide angiography at 6 to 8 weeks after CABG. There was a good correlation (r=.85, P<.001) between the quantified sestamibi activity and the extent of viable myocardium determined morphometrically. Among 21 biopsied dyssynergic myocardial segments, 11 improved their function after CABG and 10 failed to improve. Biopsied segments with improved postoperative function had significantly higher sestamibi activity (81+/-5% versus 49+/-16%, P<.0001) and significantly lower extent of interstitial fibrosis (7+/-4% versus 31+/-21%, P=.0002) than segments that failed to improve. A 55% threshold of 99mTc-sestamibi activity had positive and negative predictive values of 79% and 100%, respectively, for recovery of function after CABG in the biopsied segments. CONCLUSIONS: Myocardial 99mTc-sestamibi activity correlates well with the extent of viable myocardium and predicts improvement in regional function after CABG. This lends support to the use of sestamibi as a myocardial viability agent.

Hemodynamic effects of different pacing ratios in chronic dynamic double cardiomyoplasty.

BACKGROUND: Dynamic cardiomyoplasty is being used clinically worldwide, and evaluated by a clinical trial (phase III) in the United States. Some centers stimulate the skeletal muscle wrap with every heart beat (1:1 [muscle:heart]), whereas others use every other heart beat (1:2). Recent concern over the possible deleterious effects of too-frequent stimulation of the muscles motivated the attempt to evaluate, in a canine model of chronic, double cardiomyoplasty, the effects of two different pacing ratios on several hemodynamic parameters of interest. METHODS: Double cardiomyoplasty was performed using both latissimus dorsi muscles in 11 dogs. Fatigue resistance was achieved using the clinical transformation protocol. At a final experiment, acute cardiac failure was induced by administration of propranolol. Hemodynamic measurements of eight physiologic variables were averaged over complete pacing cycles, including the nonpaced beat at a 1:2 pacing ratio. RESULTS: The net effects of latissimus dorsi muscle stimulation at each of two pacing ratios were compared using nonparametric statistics. With the exception of left ventricular pressure (p = 0.0262) and its first derivative, dP/dt (p = 0.0099), there was no significant difference between hemodynamic performance at the two pacing ratios. CONCLUSIONS: In this canine model, pacing every other beat produces hemodynamic results that are statistically similar to pacing every beat. Less frequent stimulation of the latissimus dorsi muscle may preserve its function and improve clinical results without compromising hemodynamic benefit.

Undersensing of the tiny QRS complexes that emerged after the isolation of the right ventricle in a patient with ventricular tachycardia.

This article describes a patient who underwent right ventricular disconnection for medically refractory ventricular tachycardia associated with arrhythmogenic right ventricular dysplasia. After the operation there was no ventricular tachycardia recurrence. Two years after the operation, he received a permanent VVI pacemaker for the symptomatic second-degree AV block. Sensing function of the pacemaker was normal for the normal QRS complexes, but the tiny QRS complexes that appeared after the arrhythmia surgery were not sensed by the pacemaker and therefore caused no problem.

Transesophageal echocardiographic features and management of retained intracardiac air in two patients after surgery.

Intracardiac residual air after open-heart surgery may carry a significant risk of embolization with associated morbidity and death. We hereby report two cases of retained intracardiac air detected in an unusual location with transesophageal echocardiography in the superior aspect of the left atrium after completion of standard air-evacuation procedures. Characteristic echocardiographic features and the impact on immediate management are described along with a review of the literature.

Spreading properties of dimyristoyl phosphatidylcholine at the air/water interface.

The spreading behavior of bulk lipid crystals and lipid dispersed in water has been investigated for dimyristoyl phosphatidylcholine at the air/water interface. The stable surface pressures reached with dispersed lipid were found to increase with lipid concentration up to a concentration of approximately 1.2 mg ml-1 where the spreading pressure approached 45 mN m-1, the value for excess lipid crystals placed on the surface (at 30.5 degrees C). These low surface pressures obtained with dispersions are attributed to the existence of 'pre-equilibria': surface pressures that appear steady because of the extremely slow approach to final equilibrium. Attainment of this pre-equilibrium condition usually takes about 20 h, whereas bulk crystals held at the surface generated a high and steady surface pressure within about 1 h. Hydration of the bulk lipid slows down the spreading rate, but does not affect the final surface pressure.

Arterial lesions associated with medial disorganization and fibrosis in endomyocardial biopsies from human cardiac allografts.

We describe distinctive arterial lesions in endomyocardial biopsies from patients with human cardiac allografts. The lesions affected principally the media of small arteries and consisted of misorientation of smooth muscle cells and fibrosis. This remodelling was most prevalent in the subadventitial zone, but sometimes extended to involve the full thickness of the media. In the most extreme cases medial smooth muscle cells ran parallel to the long axis of the vessel and were segregated into small bundles and single cells separated by collagen which merged with the adventitial fibrosis. The intima was always normal. Abnormal arteries were present in 16% of 603 consecutive biopsies from 44 patients, and 39% of lesions occurred in 16% of patients. No lesions were found in endomyocardial biopsies from 25 non-transplanted patients, nor in mucosal biopsies from both transplanted and non-transplanted patients, confirming that the appearances were not due to biopsy artefact. There was early arterial remodelling in biopsies within two weeks of transplantation and none of the stages resembled vascular rejection. Fifty per cent of biopsies from some patients contained arterial lesions, suggesting that in susceptible patients they are common.

Evolution of surgical techniques for aneurysms of the descending thoracic aorta: twenty-nine years experience with 659 patients.

Between 1953 and 1993, 659 patients underwent descending thoracic aneurysm resection. The most common etiology was atherosclerosis. Pain was the main presenting symptom. Perioperative mortality fell from 24.2% between 1953 and 1964 to 14.3% between 1970 and 1993. Paraplegia occurred in 4.1% (27/659) patients overall and was little affected by time of operation or use of atriofemoral bypass. Paraparesis occurred in 5.9% (39/659) patients and was reduced by use of atriofemoral bypass. The low rate of paraparesis in the earlier experience was offset by the higher perioperative mortality from hemorrhage, attributable to the use of systemic heparin. The use of heparin-free circuits with centrifugal pumps should be considered in patients likely to have a clamp time greater than 30 minutes. The major source of perioperative morbidity and mortality was cardiac causes (48%) followed by perioperative hemorrhage (14.4%), pulmonary complications (14.4%), and rupture of another aneurysmal segment (12.0%). Late mortality occurred most commonly from cardiac causes (30.6% of deaths) and rupture of another aneurysm (16.3% of deaths). Improvement in results was due to general refinements of management in all areas rather than any single factor. These results indicate that complete preoperative assessment of the patient and the entire aorta is essential and that regular life-long follow-up is critical in order to avoid unnecessary morbidity and mortality from cardiac, cerebrovascular, or subsequent aneurysmal complications.

Acute impairment of coronary blood flow by dynamic cardiomyoplasty.

The aim of this study was to quantify the effects of three different configurations of cardiomyoplasty on coronary blood flow in an acute dog model. Thirteen dogs had both latissimus dorsi muscles harvested and transposed to the chest. Coronary blood flow was measured using Doppler cuff probes on the left anterior descending and circumflex coronary arteries during each of three cardiomyoplasty configurations: left posterior, right anterior, and double. Multiple beat measures were made of systolic and diastolic flow during a control protocol and a subsequent protocol with the muscle(s) paced. Significant flow reductions during pacing were observed in the left anterior descending coronary artery during left posterior (17%, p = 0.003), right anterior (29%, p < 0.0001), and double (35%, p = 0.0001) myoplasty. Similar reductions occurred in the circumflex artery (14%, p = 0.0009; 20%, p = 0.001; 27%, p = 0.0053). The net flow over an entire pacing cycle also was reduced significantly: left anterior descending artery (11%, p = 0.0035; 23%, p = 0.0001; 23%, p = 0.0047) and circumflex artery (10%, p = 0.0025; 17%, p = 0.0018; 21%, p = 0.0091). Thus, in the acute setting cardiomyoplasty depresses coronary blood flow. A chronic setting will be needed to determine the ultimate significance of these results.

New configuration of double cardiomyoplasty based on studies of the length-tension properties of the latissimus dorsi muscle.

A new configuration of double cardiomyoplasty was designed according to studies of the length-tension properties of the linear latissimus dorsi muscle. Four dogs had both their right and left latissimus dorsi muscles dissected from the chest wall and attached to a tensiometer to measure force of contraction. The maximum active tension obtained with stimulation of the linear latissimus dorsi muscle was observed when the muscle was at its resting anatomic length and up to 5% above this length. Eight dogs had a double cardiomyoplasty in which the resting anatomic length of both muscles was maintained. Control hemodynamic parameters obtained with the muscles at rest were compared with stimulated muscle protocols. In a normal heart state, stimulation of the double cardiomyoplasty increased the cardiac output 32% (p < 0.05), the stroke volume 39% (p < 0.05), and the left ventricular pressure 42% (p < 0.05). When acute heart failure was induced with high-dose intravenous propranolol (5 mg/kg), stimulation of the double cardiomyoplasty increased the cardiac output 32% (p = 0.01), the stroke volume 32% (p < 0.05), rate of pressure rise 39% (p < 0.01), and myocardial thickening 39% (p < 0.01). The study demonstrated that this configuration of double cardiomyoplasty provides significant hemodynamic assistance in the normal and acutely failing canine heart.

Long-term fate of the aortic root and aortic valve after ascending aneurysm surgery.

OBJECTIVE: The authors determined in which patients tube graft replacement could be used. SUMMARY BACKGROUND DATA: Tube graft replacement of ascending aortic aneurysms requires no coronary anastomoses and preserves the native aortic valve, but aortic insufficiency or aortic root aneurysms may develop requiring reoperation. Use of Bentall or Cabrol composite valve graft procedures obviates these problems but requires prosthetic valve replacement and coronary reattachment, both of which are associated with complications. These two procedures have been applied increasingly but because of renewed interest in aortic valve preservation and reconstruction, the authors determined in which patients tube replacement could be used. METHODS: The authors analyzed the fate of 277 patients, mean age 49 +/- 14 years, operated on between 1953 and 1992 by techniques that preserved the aortic root. The most common pathology was atherosclerosis in 104 patients. Perioperative mortality since 1975 was 14%. RESULTS: Fifteen patients required reoperation on the ascending aorta or aortic root; ascending aneurysm reoperation (6 patients); aortic valve replacement (8 patients), and a combined procedure (1 patient). Of these 15 patients, 8 had Marfan's syndrome, 10 had dissections, and 5 had medial degeneration/necrosis. CONCLUSIONS: Simple tube graft replacement of the ascending aorta was a durable technique in patients without Marfan's syndrome or medial degeneration/necrosis and allowed preservation of the native aortic valve in many patients.