Biomedical subjects

P A Chang

Publications and source records attributed to P A Chang.

11 recordsLinked to original sources

PubMed2001

Modified Norwood operation for hypoplastic left heart syndrome.

BACKGROUND: We examined early results in infants with hypoplastic left heart syndrome undergoing the Norwood operation with perioperative use of inhaled nitric oxide and application of extracorporeal membrane oxygenation. METHODS: Medical records were reviewed retrospectively. RESULTS: Between April 1997 and March 2001, 50 infants underwent a modified Norwood operation for hypoplastic left heart syndrome. Mean age at operation was 7.5 +/- 5.7 days, and mean weight was 3.1 +/- 0.5 kg. Five infants had a delayed operation because of sepsis. The mean diameter of the ascending aorta by echocardiography was 3.6 +/- 1.8 mm. Ductal cannulation was used to establish cardiopulmonary bypass in all patients. Mean circulatory arrest time was 39.4 +/- 4.8 minutes. The size of the pulmonary-systemic shunt was 3.0 mm in 6 infants, 3.5 mm in 37, and 4.0 mm in 7. Infants with persistent hypoxia (partial pressure of oxygen < 30 mm Hg) received nitric oxide after they were weaned from cardiopulmonary bypass. Extracorporeal membrane oxygenation was initiated in 8 infants in the pediatric intensive care unit primarily for low cardiac output and in 8 in the operating room because of the inability to separate them from cardiopulmonary bypass. The 30-day mortality rate was 22% (11 of 50 patients), and the hospital mortality rate was 32% (16 of 50 patients). Mean follow-up was 17 months. Ten patients (20%) underwent stage-two repair, with one operative death. One survivor had a Fontan procedure, and 2 underwent heart transplantation, with one death. CONCLUSIONS: Early application of extracorporeal membrane oxygenation for hemodynamic instability and selective use of nitric oxide for persistent hypoxia in the immediate postoperative period may improve survival of patients with hypoplastic left heart syndrome. Renal failure requiring hemofiltration during extracorporeal membrane oxygenation (p < 0.05) and cardiopulmonary arrest in the pediatric intensive care unit (p < 0.05) were predictors of hospital mortality.

Administration, Inhalation↗

PubMed2001

Extracorporeal membrane oxygenation in children after repair of congenital cardiac lesions.

BACKGROUND: The purpose of this study was to review our experience in the early application of extracorporeal membrane oxygenation (ECMO) in patients requiring mechanical assistance after cardiac surgical procedures. METHODS: The hospital records of all children requiring ECMO after cardiac operation were retrospectively reviewed, and an analysis of variables affecting survival was performed. RESULTS: Fifty pediatric patients between May 1997 and October 2000 required ECMO for cardiopulmonary support after cardiac operation. Patients ranged in age from 1 day to 11 years (median age, 40 days). Forty-eight patients underwent repair of congenital cardiac lesions and 2 were included after receiving a heart transplant. Twenty-two children could not be weaned from cardiopulmonary bypass and were placed on ECMO in the operating room for circulatory support. Of the 28 children who required ECMO in the intensive care unit, 10 had ECMO instituted after cardiopulmonary arrest (mean cardiopulmonary resuscitation time 42 minutes; range, 5 to 110 minutes). In infants with single-ventricle physiology, survival to discharge was 61% (11 of 18 patients) as compared with 43% (14 of 32 patients) in those with biventricular physiology. Thirty of the 50 patients (60%) were successfully weaned from ECMO, of which 25 (83%) were discharged home. Overall survival to discharge in the entire cohort was 50%. Extracorporeal membrane oxygenation support greater than 72 hours was a grave prognostic indicator. Overall survival in this group was 36% (9 of 25 patients) compared with 56% (14 of 25 patients) in those with ECMO support less than 72 hours (p < 0.05). Univariate analysis revealed the presence of renal failure, extended periods of circulatory support, and a prolonged period of cardiopulmonary resuscitation as risk factors for mortality. The presence of shunt-dependent flow, operative procedure, and institution of ECMO in the intensive care unit did not alter survival. CONCLUSIONS: Extracorporeal membrane oxygenation provides effective support for postoperative cardiac and pulmonary failure refractory to medical management. Early institution of ECMO may decrease the incidence of cardiac arrest and end-organ damage, thus increasing survival in these critically ill patients.

Child↗

PubMed1996

Evidence of improved microvascular perfusion when using antegrade and retrograde cardioplegia.

BACKGROUND: The maximum degree of microvascular distribution of cardioplegic solution is considered important to achieve optimum myocardial protection. This study attempts to demonstrate that the addition of retrograde cardioplegia to antegrade cardioplegia improves overall microvascular perfusion. METHODS: Explanted human hearts (n = 6) were treated with cold cardioplegic arrest and bicaval cardiectomy. Blood cardioplegia (37 degrees C) containing colored microspheres (color A for antegrade, color B for retrograde) was simultaneously infused antegrade at a pressure of 80 mm Hg and retrograde at a pressure of 40 mm Hg for 2 minutes. The ventricular myocardium was then sampled at three sites to determine absolute and relative cardioplegic microvascular flow. RESULTS: Of the total microvascular capillary flow, 27% to 32% was found to be the contribution of retrogradely delivered cardioplegia. CONCLUSIONS: Despite being delivered simultaneously and at a lower pressure, retrograde cardioplegia contributed substantially to overall microvascular perfusion. This suggests that antegrade cardioplegia alone does not perfuse all available myocardial capillaries and that the addition of retrograde cardioplegia enhances overall microvascular distribution and perfusion.

Cardioplegic Solutions↗

PubMed1996

L-arginine administration during reperfusion improves pulmonary function.

BACKGROUND: Nitric oxide is crucial to the maintenance of vascular homeostasis. Because nitric oxide levels decline upon lung reperfusion, infusion of L-arginine, a nitric oxide precursor, during reperfusion might prove effective at ameliorating reperfusion injury. METHODS: Neonatal piglet heart-lung blocks were preserved with Euro-Collins solution for 12 hours, rewarmed at room temperature for 1 hour, and reperfused for 10 minutes with either whole blood (n = 5), whole blood containing L-arginine (10 mmol/L; n = 6), or leukocyte-depleted blood (n = 6) on an isolated, blood-perfused, working heart-lung circuit. After the initial 10 minutes, all blocks received whole blood for 4 hours. Control blocks were continuously perfused on the circuit without intervening ischemia (n = 6). RESULTS: The partial pressure of oxygen in the whole blood group (113.8 +/- 33.1 mm Hg) was significantly less than in controls (417.3 +/- 6.2 mm Hg; p < 0.01). Lung compliance was significantly less in the whole blood group (0.8 +/- 0.2 mL/cm H2O) than in controls (2.9 +/- 0.4 mL/cm H2O; p < 0.01). The L-arginine and leukocyte-depleted blood groups showed no significant difference from controls. CONCLUSIONS: L-Arginine infusion during reperfusion improves pulmonary function, making it a simple alternative to leukocyte depletion.

Animals↗

PubMed1995

Can improved microvascular perfusion be achieved by using both antegrade and retrograde cardioplegia?

BACKGROUND: The complete and uniform distribution of cardioplegia to the microvasculature of the heart is considered critical for myocardial protection. This study explores the hypothesis that enhanced microvascular perfusion can be achieved by using both antegrade and retrograde cardioplegia. METHODS: Infant piglet hearts (n = 15) were arrested with antegrade blood cardioplegia, excised, and fixed with 2.5% glutaraldehyde by retrograde perfusion. Hearts were then perfused retrograde with an inert intracapillary marker (NTB-2). Six of these hearts served as controls (group 1) to anatomically demonstrate the degree of capillary perfusion achieved by the retrograde delivery route. Nine experimental hearts (group 2) underwent a subsequent infusion of antegrade blood cardioplegia to wash out NTB-2 capillaries coperfused by both the antegrade and retrograde delivery techniques. Sections of the left ventricular free wall and anterior-mid interventricular septum were taken and examined by light microscopy at four separate sites (average, 126 capillaries per section). RESULTS: In control hearts, 91.9% +/- 0.9% of ventricular capillaries and 91.4% +/- 5.8% of septal capillaries were perfused by retrograde cardioplegia. After antegrade blood cardioplegia washed out group 2 hearts, 14.0% +/- 4.1% of capillaries in the ventricle still contained NTB-2, as did 12.5% +/- 5.4% of capillaries in the septum. CONCLUSIONS: In this experimental model, antegrade blood cardioplegia did not coperfuse (and therefore washout) 12.5% to 14% (p < 0.05) of capillaries perfused by retrograde cardioplegia. This suggests that an additional 12.5% to 14% of capillaries within the myocardium may receive cardioplegia if retrograde cardioplegia is used in addition to antegrade cardioplegia. We conclude that by combining both antegrade and retrograde cardioplegia, there is a potential for enhanced overall microvascular perfusion.

Animals↗

PubMed1994

Fumarate-enriched blood cardioplegia results in complete functional recovery of immature myocardium.

Amino acid enrichment of cardioplegic solutions has been shown to improve both the metabolic and functional recovery of ischemic myocardium. However, because of the marked systemic vasodilatation involved, use of amino acid enrichment is limited to the periods of induction and reperfusion. Fumarate is a Krebs' cycle intermediate whose conversion to succinate is responsible for the generation of adenosone triphosphate and the oxidation of the reduced form of nicotinamide-adenine nucleotide which is the pathway by which aspartate exerts its effect. Fumarate may also function as a free-radical scavenger and is involved in calcium transport. To determine if fumarate-enriched blood cardioplegia would improve the functional recovery of the neonatal heart, 14 neonatal piglet hearts were isolated and placed on a blood-perfused working heart circuit. After the baseline functional and metabolic assessment was done, cold ischemic arrest was initiated with either standard blood cardioplegic solution (group I; N = 7) or fumarate-enriched (13 mmol/L) blood cardioplegic solution (group II; N = 7). Cardioplegic solution was given at a pressure of 40 mm Hg every 20 minutes for 2 hours, and topical hypothermia was used. Sixty minutes after warm whole blood reperfusion, the functional recovery at left atrial pressures of 3, 6, 9, and 12 mm Hg was 70%, 66%, 66%, and 65%, respectively, in group I, versus 102%, 106%, 105%, and 109%, respectively, in group II (p < 0.05). The tissue creatinine phosphate levels after reperfusion were significantly higher in group II hearts (15.0 +/- 1.2 mumol/g dry heart tissue) than in group I hearts (9.2 +/- 1.9 mumol/g dry heart tissue), although the adenosine triphosphate levels were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1994

Spontaneous closure of fenestrations in an interatrial Gore-Tex patch: application to the Fontan procedure.

The concept of the partial Fontan procedure, first described with the adjustable atrial septal defect (ASD) and more recently with the fenestrated technique, has become an accepted approach for the management of high-risk patients undergoing the Fontan procedure. Experience with both techniques has shown that a patent ASD placed in a prosthetic interatrial baffle may close spontaneously over a period of weeks to months. The mechanism and timing of spontaneous closure, as well as the effect of antiplatelet therapy on this process, are poorly understood. To better define this process, the interatrial septum of 15 mongrel dogs was excised and replaced with a fenestrated Gore-Tex (W.L. Gore, Flagstaff, AZ) patch. Postoperative echocardiography confirmed the patency of the ASD and left-to-right shunting. Animals were sacrificed 4 to 6 weeks postoperatively, or sooner if infection or other postoperative complications developed. Eight animals underwent no antiplatelet or anticoagulation therapy postoperatively, and 7 received antiplatelet therapy with aspirin. Patches were removed at the end of the study period and analyzed. By 6 weeks, all 2.7-mm and 4-mm holes had closed spontaneously in all animals that had not received antiplatelet therapy. The earliest closure occurred at 1 week. With antiplatelet therapy, hole closure was found to be delayed but not prevented, and was complete by 6 weeks in all but 1 animal. Histologic examination of the explanted patches revealed that closure was accomplished primarily through the ingrowth of fibrous tissue, accompanied by an inflammatory cell infiltrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Girdling effect of nonstimulated cardiomyoplasty on left ventricular function.

The precise hemodynamic effects of latissimus dorsi cardiomyoplasty have not been well characterized. We prospectively studied 11 mongrel dogs using a rapid ventricular pacing model of congestive heart failure. Six dogs received a nonstimulated left latissimus dorsi cardiomyoplasty wrap, and 5 control dogs were paced only. Two-dimensional transthoracic echocardiography was performed on all dogs at baseline and then weekly for 4 weeks. Measurements obtained included left ventricular diameters, lengths, volumes, and ejection fractions. Progressive left ventricular enlargement, increase in volumes, and worsening ejection fractions developed in both groups. However, less left ventricular dilatation and higher ejection fractions were seen in dogs that received a cardiomyoplasty wrap. A nonstimulated cardiomyoplasty wrap significantly attenuated the degree of left ventricular enlargement, increase in left ventricular volumes, and decrease in ejection fraction in a rapid pacing model of congestive heart failure. Apart from its effect on systolic augmentation with a stimulated muscle wrap, cardiomyoplasty may have an important "girdling" effect on the left ventricle that prevents dilatation and deterioration of left ventricular function.

Animals↗

PubMed1993

Gross and microvascular distribution of retrograde cardioplegia in explanted human hearts.

In this report, explanted hearts from transplant recipients with the diagnosis of idiopathic cardiomyopathy underwent a blood cardioplegia arrest and extended subatrial resection to preserve their coronary sinus venous system. The coronary sinus and left and right coronary arteries were then cannulated and warm blood cardioplegia retrograde infused at a pressure of 30 to 40 mm Hg. Effluent from the coronary arteries and thebesian veins was then collected. Hearts were subsequently fixed with retrograde glutaraldehyde perfusion and perfused retrograde with NTB-2 (an inert intracapillary marker). Histologic sections were examined from 12 separate sites. There was no significant difference in the percentage of capillaries perfused by retrograde-delivered cardioplegia between corresponding regions of the left and right ventricles. However, effluent analysis indicated that 67.2% +/- 6.4% of retrograde-delivered blood cardioplegia was shunted through thebesian veins, thereby bypassing the microvasculature, whereas 29.3% +/- 6.3% and 3.5% +/- 3.1% traversed the myocardium supplied by the left and right coronary arteries, respectively. The results indicate that all regions of both ventricles are perfused by retrograde blood cardioplegia. However, they also suggest that nutrient flow to the microvasculature of the right ventricle is minimal during retrograde cardioplegia.

Blood↗

PubMed1992

Fluosol cardioplegia results in complete functional recovery: a comparison with blood cardioplegia.

Blood cardioplegia is considered by many to be the preferred solution for myocardial protection. Proposed benefits include the ability to deliver oxygen and the ability to maintain metabolic substrate stores. However, the decreased capacity of blood to release oxygen at hypothermic conditions as well as the presence of deleterious leukocytes, platelets, and complement may limit complete functional recovery. Fluosol is an asanguineous solution with the ability to bind and release oxygen linearly at low temperatures. Neonatal piglet hearts (24 to 48 hours old) were excised and supported on an isolated, blood-perfused working heart model. After baseline stroke-work index was determined, hearts were arrested with either normocalcemic blood cardioplegia (group 1, n = 8) or normocalcemic Fluosol cardioplegia (group 2, n = 8). Cold cardioplegia was administered at 45 mm Hg every 20 minutes for 2 hours. Hearts were then reperfused with whole blood. Functional recovery, expressed as percent of control stroke-work index, was determined 60 minutes after reperfusion at left atrial pressures of 3, 6, 9, and 12 mm Hg. Functional recovery at 60 minutes was similar between group 1 (95%, 93%, 93%, 88%) and group 2 (100%, 94%, 94%, 95%) at left atrial pressures of 3, 6, 9, and 12 mm Hg, respectively. Mean lactate consumption 5 minutes after reperfusion was significantly greater (p = 0.0001) in group 1 (31.8 +/- 6.3 micrograms.min-1 x g-1) than in group 2 (-0.59 +/- 0.1 microgram.min-1 x g-1), indicating superior metabolic recovery in the blood cardioplegia hearts. Edema formation, as determined both by water content (group 1, 81.10%; group 2, 81.63%) and by electron microscopy, was not significantly different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1988

Effects of acute hypoxia and reoxygenation in a blood-perfused neonatal heart model.

Newborn (less than 4-day old) piglet hearts (n = 7) were isolated and perfused with blood from a support pig. With use of a reservoir and membrane oxygenator, each heart was perfused for 90 minutes with blood at an O2 saturation of 40% and a pH of 7.4-7.5, at a left atrial pressure of 9 mm Hg, and at an aortic root pressure of 80 mm Hg. Blood saturation was increased to 100%, and the left atrial pressure decreased to 6 mm Hg for 60 minutes. Minute work indexes were calculated for each heart before hypoxia, every 30 minutes during hypoxia, and at 30 and 60 minutes of reoxygenation. Control hearts (n = 8) were treated in an identical fashion, but O2 saturation was maintained at 100%. Myocardial function decreased in the neonatal hearts exposed to hypoxia and reoxygenation. Control hearts did not suffer any significant decrease in function. Nucleotide levels were similar in both groups at the completion of the experiment. Anaerobic metabolism was demonstrated in the hypoxic hearts by net release of lactic acid during the period of hypoxia. This model can be used to study methods of intervention in the working hypoxic neonatal heart.

Acute Disease↗