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Biomedical subjects

G J Vlahakes

Publications and source records attributed to G J Vlahakes.

At least 19 recordsLinked to original sources
PubMed1998

Slide tracheoplasty for long-segment tracheal stenosis.

OBJECTIVE: To introduce a novel surgical technique for the repair of congenital long-segment tracheal stenosis. DESIGN: Retrospective case series. SETTING: Tertiary-care hospital. PATIENTS: Three children ranging in age from 3 months to 3 years, all with complete tracheal rings, the stenotic segments representing between 36% and 49% of the total tracheal length. One patient had an anomalous right upper lobe bronchus and an associated pulmonary artery sling. INTERVENTION: Slide tracheoplasty reconstruction. MAIN OUTCOME MEASURE(S): Postoperative clinical status as evidenced by day and site of extubation, duration of hospitalization, number of bronchoscopic examinations performed before discharge, and subsequent need for urgent bronchoscopic examinations, which reflects the adequacy of the reconstructed airway. RESULTS: Two patients were extubated on the day of surgery, 1 intraoperatively; the child with the pulmonary artery sling required 3 days of elective intubation for postoperative ventilatory support. The duration of hospitalization ranged from 8 to 10 days. All patients underwent elective bronchoscopy once before discharge; none had granuloma formation. Follow-up ranged from 1 to 4 1/2 years. One patient required a single urgent bronchoscopic examination in addition to planned surveillance endoscopy. Growth of the reconstructed hemitracheal rings is demonstrable. CONCLUSIONS: Slide tracheoplasty achieves successful tracheal reconstruction using the patient's own tracheal tissues. Advantages of this method include the potential avoidance of cardiopulmonary bypass, immediate or early postoperative extubation, and the near-complete absence of granulation tissue formation. The latter obviates the need for multiple postoperative bronchoscopic examinations, as has been reported in tracheoplasty procedures using either costal cartilage or pericardium.

Child, Preschool↗
PubMed1998

Risk of reoperative valve replacement for failed mitral and aortic bioprostheses.

BACKGROUND: One factor influencing the choice of mechanical versus bioprosthetic valves is reoperation for bioprosthetic valve failure. To define its operative risk, we reviewed our results with valve reoperation for bioprosthetic valve failure. METHODS: Records of 400 consecutive patients having reoperative mitral, aortic, or mitral and aortic bioprosthetic valve replacement from January 1985 to March 1997 were reviewed. RESULTS: Reoperations were for failed bioprosthetic mitral valves in 219 patients, failed aortic valves in 153 patients, and failed aortic and mitral valves in 28 patients. Including 26 operations (6%) for acute endocarditis, 153 operations (38%) were nonelective. One hundred nine patients (27%) had other valves repaired or replaced, and 72 (18%) had coronary bypass grafting. The incidence of death in the mitral, aortic, and double-valve groups was respectively, 15 (6.8%), 12 (7.8%), and 4 (14.3%); and the incidence of prolonged postoperative hospital stay (>14 days) was, respectively, 57 (26.0%), 41 (26.8%), and 8 (28.6%). Only 7 of 147 patients (4.8%) having elective, isolated, first-time valve reoperation died. Multivariable predictors (p < 0.05) of hospital death were age greater than 65 years, male sex, renal insufficiency, and nonelective operation; and predictors of prolonged stay were acute endocarditis, renal insufficiency, any concurrent cardiac operation, and elevated pulmonary artery systolic pressure. CONCLUSIONS: Reoperative bioprosthetic valve replacement can be performed with acceptable mortality and hospital stay. The best results are achieved with elective valve replacement, without concurrent cardiac procedures.

Adult↗
PubMed1998

Repeat aortic root replacement.

BACKGROUND: Aortic root replacement in patients who have undergone previous aortic root replacement presents a formidable technical challenge, which may lead to increased surgical mortality. METHODS: We reviewed our experience from January 1989 through November 1995. Seven consecutive patients (6 men and 1 woman) underwent eight repeat aortic root replacements. Mean follow-up was 19 months. Previous root replacement had been performed with homograft in 1 patient, with a bioprosthetic valve composite graft in 1 patient, and with a mechanical valve composite graft in 6 patients. The techniques used at the previous procedures were the Cabrol technique (2 patients), Bentall technique (3 patients), and the coronary button technique (3 patients). Reoperation was indicated for pseudoaneurysm formation in 4 patients and for endocarditis in the others. RESULTS: Aortic homografts were implanted in all patients with endocarditis and mechanical valve composite grafts were used in the others. In all reoperations, the coronary button technique was used. No procedures were done emergently. Concomitant procedures were performed in 2 patients, including mitral valve replacement and aortic arch aneurysm repair. One patient had recurrence of his endocarditis 36 months after operation because of continued intravenous drug use requiring a second successful homograft root replacement. There were no early deaths and one late death at 16 months after operation. CONCLUSIONS: Repeat aortic root replacement, even in the setting of endocarditis, can be done with low mortality.

Adult↗
PubMed1998

Contribution of the interventricular septum to maximal right ventricular function.

OBJECTIVE: Maximal right ventricular (RV) function is influenced by left heart hemodynamics, possibly mediated by the interventricular scpturn (IVS). We examined the potential contribution of the IVS function to right heart function. METHODS: In 12 canine isovolumic right heart preparations, incremental volumes were introduced into a high compliance RV balloon until RV failure occurred. Maximal RV developed pressure (RVDP) and maximal positive RV dP/dt were determined with a working IVS at a constant left ventricular (LV) output of 2 l/min and at a constant mean arterial pressure of 80 mmHg. Thereafter the IVS was thermally inactivated, and measurements were repeated using the same protocol. RESULTS: At constant arterial pressure and constant LV output, thermal inactivation of the IVS led to a significant decrease in maximal RVDP (inactivated vs. working IVS: 36.1+/-9.8 vs. 56.8+/-16.2 mmHg, respectively, P < 0.001), and RV dP/dt (inactivated vs. working IVS: 720+/-220 vs. 1350+/-190 mmHg/s, respectively, P < 0.001). CONCLUSIONS: These results suggest that the functional status of the IVS is a major determinant of maximal RV function. At constant LV conditions and arterial pressure, an inactivated IVS leads to a significant decrease in maximal RVDP and RV dP/dt under the conditions of this study.

Animals↗
PubMed1997

Insights from three-dimensional echocardiography into the mechanism of functional mitral regurgitation: direct in vivo demonstration of altered leaflet tethering geometry.

BACKGROUND: Recent advances in three-dimensional (3D) echocardiography allow us to address uniquely 3D scientific questions, such as the mechanism of functional mitral regurgitation (MR) in patients with left ventricular (LV) dysfunction and its relation to the 3D geometry of mitral leaflet attachments. Competing hypotheses include global LV dysfunction with inadequate leaflet closing force versus geometric distortion of the mitral apparatus by LV dilatation, which increases leaflet tethering and restricts closure. Because geometric changes generally accompany dysfunction, these possibilities have been difficult to separate. METHODS AND RESULTS: We created a model of global LV dysfunction by esmolol and phenylephrine infusion in six dogs. initially with LV expansion limited by increasing pericardial restraint and then with the pericardium opened. The mid-systolic 3D relations of the papillary muscle (PM) tips and mitral valve were reconstructed. Despite severe LV dysfunction (ejection fraction, 18+/-6%), only trace MR developed when pericardial restraint limited LV dilatation; with the pericardium opened, moderate MR accompanied LV dilatation (end-systolic volume, 44+/-5 mL versus 12+/-5 mL control, P<.001). Mitral regurgitant volume and orifice area did not correlate with LV ejection fraction and dP/dt (global function) but did correlate with changes in the tethering distance from the PMs to the anterior annulus derived from the 3D reconstructions, especially PM shifts in the posterior and mediolateral directions, as well as with annular area (P<.0005). By multiple regression, only changes in the PM-to-annulus distance independently predicted MR volume and orifice area (R2=.82 to .85, P=2x10(-7) to 6x10(-8)). CONCLUSIONS: LV dysfunction without dilatation fails to produce important MR. Functional MR relates strongly to changes in the 3D geometry of the mitral valve attachments at the PM and annular levels, with practical implications for approaches that would restore a more favorable configuration.

Animals↗
PubMed1997

A new, biventricular working heterotopic heart transplant model: anatomic and physiologic considerations.

BACKGROUND: Current heterotopic heart transplant models have nonworking left ventricles that atrophy and are not suitable for some studies. We developed and characterized a new heterotopic model with working left and right ventricles. METHODS: Hemodynamics were compared in the working and nonworking models. The influence of the length of the donor's aorta on coronary arterial oxygenation was tested. The influence of the recipient's arterial pressure on developed left ventricular systolic pressure and the effects of alpha- and beta-adrenergic stimulation were examined in both models. The nonworking and working models were compared in chronic transplant preparations to investigate possible ventricular atrophy. RESULTS: In this model, coronary arterial oxygen tension was influenced by the length of the donor's aorta. With a short donor aorta (0.5 cm in the porcine model), normal coronary arterial oxygenation is maintained. Left ventricular systolic pressure was greater in the working compared with the nonworking models. Left ventricular systolic pressure did not respond to alpha-adrenergic stimulation but did respond to beta-adrenergic and combined stimulation, which indicates its relationship to donor heart output. Left ventricular systolic pressure correlated with and was determined by recipient arterial pressure. Ventricular atrophy occurred in the nonworking model, but ventricular weight was maintained at sham control levels in this new working model. CONCLUSION: These results demonstrate the surgical anatomic considerations of a new heterotopic heart transplant model in which the left and right ventricles work. Its hemodynamic performance is related to recipient hemodynamics, and the model responds to adrenergic stimulation. In chronic studies, ventricular mass is maintained, thus allowing this model to overcome a significant shortcoming of existing heterotopic heart transplant models.

Animals↗
PubMed1997

Cardiac operations in patients 80 years old and older.

BACKGROUND: Because the elderly are increasingly referred for operation, we reviewed results with cardiac surgical patients 80 years old or older. METHODS: Records of 600 consecutive patients 80 years old or older having cardiac operations between 1985 and 1995 were reviewed. Follow-up was 99% complete. RESULTS: Two hundred ninety-two patients had coronary grafting (CABG), 105 aortic valve replacement (AVR), 111 AVR + CABG, 42 mitral valve repair/ replacement (MVR) +/- CABG, and 50 other operations. Rates of hospital death, stroke, and prolonged stay (> 14 days) were as follows: CABG: 17 (5.8%), 23 (7.9%) and 91 (31.2%); AVR: 8 (7.6%), 1 (1.0%), and 31 (29.5%); AVR + CABG: 7 (6.3%), 12 (10.8%), and 57 (51.4%); MVR +/- CABG: 4 (9.5%), 3 (7.1%), and 16 (38.1%); other: 9 (18.0%), 3 (6.0%), and 23 (46.0%). Multivariate predictors (p < 0.05) of hospital death were chronic lung disease, postoperative stroke, preoperative intraaortic balloon, and congestive heart failure; predictors of stroke were CABG and carotid disease; and predictors of prolonged stay were postoperative stroke and New York Heart Association class. Actuarial 5-year survival was as follows: CABG, 66%; AVR, 67%; AVR + CABG, 59%; MVR +/- CABG, 57%; other, 48%; and total, 63%. Multivariate predictors of late death were renal insufficiency, postoperative stroke, chronic lung disease, and congestive heart failure. Eighty-seven percent of patients believed having a heart operation after age 80 years was a good choice. CONCLUSIONS: Cardiac operations are successful in most octogenarians with increased hospital mortality, postoperative stroke, and longer hospital stay. Long-term survival is largely determined by concurrent medical diseases.

Actuarial Analysis↗
PubMed1997

Effect of recombinant human erythropoietin on transfusion risk in coronary bypass patients.

BACKGROUND: Patients having a cardiac operation frequently require allogeneic blood transfusions despite surgical blood-conservation techniques. Recombinant human erythropoietin (Epoetin alfa) may augment this conservation by stimulating erythropoiesis. The safety and efficacy of perioperative use of Epoetin alfa to reduce the need of allogeneic transfusion was studied. METHODS: A multicenter double-blind, placebo-controlled, parallel-group study involved 182 patients having coronary artery bypass grafting and randomized to receive Epoetin alfa (300 or 150 IU/kg) or placebo subcutaneously for 5 days before, on the day of, and for 2 days after operation. RESULTS: Perioperative Epoetin alfa resulted in greater increases in baseline to preoperative hemoglobin levels and hematocrit (300 IU/kg) and in presurgery to postsurgical day 1 reticulocyte counts versus placebo (p < or = 0.05). However, there was no significant difference in transfusion requirements. Incidences of adverse events were similar in all study groups. CONCLUSIONS: Lower incidences of allogeneic blood exposure were observed in both Epoetin alfa-treated groups; however, the differences between all treatment groups were not significant. This was probably due to the relatively short 5-day preoperative course of Epoetin alfa therapy. There were no significant differences between the three groups relative to safety. Epoetin alfa was well tolerated in this population.

Antibodies↗
PubMed1997

The treatment of patients with infected implantable cardioverter-defibrillator systems.

OBJECTIVE: The purpose of this study was to evaluate the treatment of patients with infected implantable cardioverter-defibrillator systems. METHODS: Retrospective analysis was done of the cases of 21 patients treated for implantable cardioverter-defibrillator infection during an 11-year period. RESULTS: Of 723 cardioverter-defibrillator implantations (550 primary implants, 173 replacements), nine (1.2%) were complicated by early postoperative device-related infections. Late infections developed in two patients 19 and 22 months, respectively, after implantation. Ten other patients were transferred to our institution for treatment of cardioverter-defibrillator infection. The time from implantation to overt infection was 2.2 +/- 1.3 months, excluding the two late infections. The responsible organisms were Staphylococcus aureus (9), Staphylococcus epidermidis (6), Streptococcus hemolyticus (1), gram-negative bacteria (3), Candida albicans (1), and Corynebacterium (1). All patients were treated with intravenous antibiotic drugs. Total system removal was done in 15 patients and partial removal in 2; in 4, the cardioverter-defibrillator system was not explanted. There were no perioperative deaths. A new implantable cardioverter-defibrillator system was reimplanted in 7 patients after 2 to 6 weeks of antibiotic therapy. Ten patients were treated without reimplantation (2 arrhythmia operation, 8 antiarrhythmic drugs). Four patients (3 patients without explantation and 1 with partial system removal) were treated with maintenance long-term antibiotic therapy. During a mean follow-up of 21 +/- 2.8 months, no patient had clinical recurrence of infection. One patient treated with antiarrhythmic drugs without system reimplantation died suddenly. CONCLUSIONS: Infections that involve implantable cardioverter-defibrillator systems can be safely managed by removing the entire system with reimplantation after intravenous antibiotic therapy. In selected patients in whom the risk for system explantation is high and anticipated life expectancy is short, long-term antibiotic therapy to suppress low-virulence infections may represent an acceptable alternative.

Adult↗
PubMed1997

Nonreplacement operations for mitral valve regurgitation.

Mitral valve reconstruction offers patients an important alternative to the traditional method for treating severe mitral regurgitation--mitral valve replacement. Over the last 15 years, surgical techniques have evolved for treating mitral regurgitation occurring from various anatomic mechanisms--annular dilatation, abnormal leaflet motion due to a variety of causes, or leaflet perforation. Currently, over 90% of regurgitant mitral valves of varying etiologies are amenable to nonreplacement therapy by reconstruction, with good intermediate- and long-term results. Reconstruction obviates the need for long-term anticoagulation, and thus, there has evolved a trend toward reconstruction earlier in the course of this disease, before fixed atrial fibrillation and ventricular dilatation occur.

Heart Valve Prosthesis↗
PubMed1996

Composite aortic root replacement with direct coronary artery implantation.

BACKGROUND: Composite aortic root replacement is accepted treatment for aneurysms of the ascending aorta involving the root with aortic valve regurgitation, but controversy continues regarding the best technique of operation. We excise the aneurysm, implant a composite valve graft, directly attach the coronary arteries to the aortic graft, and make the distal anastomosis to the divided aorta. METHODS: We reviewed the records and collected complete follow-up data on 110 consecutive patients having composite aortic root replacement with this technique from 1979 to 1995. RESULTS: Average age was 54 years. Marfan's syndrome was present in 22 patients, acute dissections in 26, chronic dissections in 11, and active endocarditis in 13. Operative characteristics were: 25 emergency procedures, 33 urgent procedures, 52 elective procedures, 24 reoperations, and 19 with coronary artery bypass grafting. Hospital death occurred in 8 patients (7.3%). Multivariate predictors of hospital death were postoperative renal failure and acute dissection. Actuarial survival was 70% at 10 years (standard error, 5%). Multivariate predictors of total mortality were porcine valve, Björk-Shiley valve, preoperative stroke, reoperation on a composite valve graft, and coronary artery bypass grafting. Only 3 patients required late reoperation, all for valve dysfunction. Actuarial freedom from reoperation on the aortic root was 97.3% (standard error, 1.9%) at 10 years. Late echocardiograms in 47 patients showed no anastomotic aneurysms. CONCLUSIONS: Composite aortic root replacement with direct coronary implantation is effective and durable treatment for a variety of aortic pathologic conditions in elective and emergency situations.

Actuarial Analysis↗
PubMed1995

Imaging and sizing of atrial septal defects by magnetic resonance.

BACKGROUND: Development of techniques for percutaneous closure of atrial septal defects (ASDs) makes accurate noninvasive sizing of ASDs important for appropriate patient selection. METHODS AND RESULTS: Magnetic resonance (MR) images of ASDs were obtained in 30 patients (mean age, 41 +/- 16 years) by both spin-echo and phase-contrast cine MR imaging. Spin-echo images were obtained in two orthogonal views (short-axis and four-chamber) perpendicular to the plane of the ASD. Spin-echo major and minor diameters were measured, and spin-echo defect area was calculated. Phase-contrast cine MR images were obtained in the plane of the ASD, and cine major diameter and defect area were measured from the region of signal enhancement or phase change due to shunt flow across the defect. MR measurements were compared with templates cut during surgery to match the defect or with ASD diameter determined by balloon sizing at catheterization. ASD size measured from cine MR images (y) agreed closely with catheterization and template standards (x). For major diameter, y = 0.78x + 5.7, r = .93, and SEE = 3.4 mm. On average, spin-echo measurements overestimated major diameter and area of secundum ASDs by 48% and 125%, respectively. CONCLUSIONS: Phase-contrast cine MR images acquired in the plane of an ASD define the defect shape by the cross section of the shunt flow stream and allow noninvasive determination of defect size with sufficient accuracy to permit stratification of patients to closure of the defect by catheter-based techniques versus surgery. Spin-echo images, on the other hand, are not adequate for defining ASD size, because septal thinning adjacent to a secundum ASD may appear to be part of the defect.

Adult↗
PubMed1995

Influence of the implantable cardioverter/defibrillator on sudden death and total mortality in patients evaluated for cardiac transplantation.

BACKGROUND: Implantable cardioverter/defibrillators (ICDs) may reduce sudden tachyarrhythmic death in patients with severe left ventricular dysfunction. It is uncertain whether this improves survival, particularly in patients awaiting cardiac transplantation. METHODS AND RESULTS: The effect of treatment for spontaneous ventricular arrhythmias (ICD [n = 59], antiarrhythmic drugs [n = 53], or no antiarrhythmic treatment [n = 179]) on total mortality and mode of cardiac death was analyzed in 291 consecutive patients evaluated for cardiac transplantation between January 1986 and January 1995. There were 109 deaths (37.4%) (63 [21.6%] sudden, 40 [13.7%] nonsudden, and 6 [2.1%] noncardiac) during mean follow-up of 15 months (range, 1 to 118 months). Baseline clinical variables, medical therapies for heart failure, and actuarial rates of transplantation were similar between treatment groups. Kaplan-Meier sudden death rates were lowest in the ICD group, intermediate in the no antiarrhythmic treatment group, and highest in the drug treatment group throughout follow-up (12-month sudden death rates, 9.2%, 16.0%, and 34.7%, respectively; P = .004). Total mortality and nonsudden death rates did not differ. Cox proportional-hazards model revealed that antiarrhythmic drug treatment was associated with sudden death (relative risk, 2.1; 95% CI, 1.04 to 3.39; P = .04) and ICD was associated with nonsudden death (relative risk, 2.26; 95% CI, 1.12 to 4.62; P = .02). CONCLUSIONS: Sudden death rates were lowest in patients treated with ICDs compared with drug treatment or no antiarrhythmic treatment. However, although ICDs reduced sudden death in selected high-risk patients with severe left ventricular dysfunction, the effect on long-term survival was limited, principally by high nonsudden death rates.

Actuarial Analysis↗
PubMed1995

Experimental ablation of outflow tract muscle with a thermal balloon catheter.

BACKGROUND: Pulmonary balloon valvuloplasty has been performed in selected patients with tetralogy of Fallot as an alternative to surgical palliation; this technique is limited, however, by the fact that the balloon has little effect on the dynamic, muscular contribution to outflow tract obstruction. In an experimental model, we used a new thermal balloon catheter to ablate right ventricular outflow tract muscle. We evaluated the acute efficacy and muscle ablation parameters of this technology and its effects after myocardial healing. METHODS AND RESULTS: A prototype electrolyte-filled balloon catheter, heated by radiofrequency energy, was constructed. Studies were conducted to determine the optimum electrolyte solution needed to minimize balloon heating time with an unmodified, commercially available radiofrequency generator. In vivo ablations of right ventricular outflow tract muscle with the thermal balloon were performed in lambs that were divided into three groups (n = 5 each) according to the duration of thermal energy delivery (20, 40, and 60 seconds, respectively). Ablated lesion volume increased (460 +/- 63 to 1156 +/- 256 mm3) as the energy delivery time increased (20 to 60 seconds) and was correlated with delivered energy, temperature integral, and maximum epicardial surface temperature (r = .85, .82, and .72, respectively). All five lesions in the 60-second group showed an acute decrease of the wall thickness. Additional in vivo ablations were performed in 6 animals in which survival studies showed muscle thinning, healing by fibrosis, and no evidence of aneurysm formation. CONCLUSIONS: Thermal energy can be used with a balloon catheter delivery system to ablate myocardium. This study suggests that this energy delivery technology might be useful for relief of muscular outflow tract obstruction and that further studies are warranted.

Animals↗
PubMed1995

Papillary muscle displacement causes systolic anterior motion of the mitral valve. Experimental validation and insights into the mechanism of subaortic obstruction.

BACKGROUND: Systolic anterior motion (SAM) of the mitral valve in hypertrophic cardiomyopathy (HCM) has generally been explained by a Venturi effect related to septal hypertrophy, causing outflow tract narrowing and high velocities. Patients with HCM, however, also have primary abnormalities of the mitral apparatus, including anterior and inward or central displacement of the papillary muscles, and leaflet elongation. These findings have led to the hypothesis that changes in the mitral apparatus can be a primary cause of SAM by altering the forces acting on the mitral valve and its ability to move in response to them. Despite suggestive observations, however, it has never been prospectively demonstrated that such changes can actually cause SAM. METHODS AND RESULTS: To test this hypothesis in vivo, anterior papillary muscle displacement was created in 7 dogs studied by echocardiography, with controlled cardiac output and heart rate. In all 7 dogs, papillary muscle displacement caused SAM, with an outflow tract gradient (33 +/- 19 mm Hg) and mitral regurgitation in 6. As in patients with HCM, the mitral valve was displaced anteriorly and the coaptation point shifted toward the insertion of the leaflets, creating longer distal residual leaflets that moved anteriorly. CONCLUSIONS: Primary changes in the mitral apparatus can cause SAM without septal hypertrophy. In this model, SAM appears to be determined by the ability of the leaflets to move anteriorly (papillary muscle displacement causing slack and increased residual leaflet length) and their interposition into the outflow stream by anterior displacement, determining the direction of this motion. Geometric factors observed in HCM and in patients with SAM without HCM can therefore play a primary role in causing SAM.

Animals↗