A K Pridjian

Concordia University‚ÄďAnn Arbor, Ann Arbor, Michigan, United States

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Publications (9)27.68 Total impact

  • A K Pridjian, E L Bove, F M Lupinetti
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    ABSTRACT: To elucidate differences in myocardial blood flow and metabolism between cyanotic and normal hearts, a model of chronic cyanosis was created in five adult mongrel dogs by anastomosing the inferior vena cava to the left atrium. After 6 to 9 months, myocardial blood flow, the ratio of subendocardial to subepicardial flow, oxygen consumption, oxygen extraction ratio, and lactate consumption in these cyanotic dogs and five control dogs were determined under baseline conditions and during pharmacologic stress with isoproterenol (0.2 micrograms/kg/min). Radioactive microspheres were used to determine left and right ventricular blood flow rates, and arterial and coronary sinus differences in oxygen and lactate levels were measured. At baseline and during stress, oxygen consumption and oxygen extraction ratios were identical in control and cyanotic hearts. Total myocardial blood flow was increased with stress and did not differ between cyanotic and control hearts. Left ventricular muscle from cyanotic hearts did exhibit lower endocardial/epicardial blood flow ratios than those of control hearts at rest, and the relative subendocardial flow decreased further with stress. During isoproterenol infusion, myocardial lactate production, indicative of anaerobic metabolism, was evident in two of five cyanotic animals and none of the control dogs. The relative subendocardial ischemia and its further aggravation by stress in cyanotic hearts may contribute to the pathophysiologic basis of myocardial dysfunction in cyanotic heart disease.
    Journal of Thoracic and Cardiovascular Surgery 06/1995; 109(5):849-53. · 3.53 Impact Factor
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    ABSTRACT: Age-related differences in the activity of 5'-nucleotidase, an enzyme responsible for conversion of high-energy phosphates to their the diffusible precursors, may help to explain age-related differences in tolerance of global myocardial ischemia. Postischemic function and high-energy phosphate content were measured in the hearts of rabbits 7 to 10 days old (neonate), 30 to 40 days old (1 month), and 6 to 12 months old (adult). Hearts in each age group were subjected to 60 minutes of ischemia at 34 degrees C either with no cardioplegia, with unmodified St. Thomas' Hospital cardioplegic solution, or with St. Thomas' Hospital cardioplegic solution with pentoxifylline, a 5'-nucleotidase inhibitor. These groups were compared with one another and with control hearts that were continuously perfused for 1 hour. In adults, addition of pentoxifylline to St. Thomas' Hospital cardioplegic solution restored adenosine triphosphate and total nondiffusible nucleotide levels to control values and improved recovery of cardiac output and developed pressure compared with results with unmodified St. Thomas' Hospital cardioplegic solution. In contrast, biochemical and functional parameters in neonatal hearts were not affected by either unmodified St. Thomas' Hospital cardioplegic solution cardioplegia or St. Thomas' Hospital cardioplegic solution with pentoxifylline. Functional recovery in neonatal hearts subjected to unprotected ischemia was superior to that in the older age groups. In 1-month-old hearts, St. Thomas' Hospital cardioplegia improved recovery compared with recovery after unprotected ischemia, but no incremental improvement in function or high-energy stores was seen with addition of pentoxifylline. The lack of effect of pentoxifylline on neonatal hearts suggest that there is a relative deficiency of 5'-nucleotidase in this age group. This may contribute to the improved functional recovery observed in unprotected hearts. Furthermore, addition of pentoxifylline to adult hearts appears to confer the benefits of low 5'-nucleotidase activity occurring naturally in the neonate.
    Journal of Thoracic and Cardiovascular Surgery 03/1994; 107(2):520-6. · 3.53 Impact Factor
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    ABSTRACT: Renal dysfunction may follow administration of iodinated radiographic contrast agents. This complication may be less common when low osmolarity nonionic agents are used. Although potential benefits from the use of low osmolarity nonionic contrast may be minimal in individuals with normal physiology, a greater benefit has been postulated in the presence of chronic cyanosis. To test this hypothesis, six adult mongrel dogs underwent anastomosis of the inferior vena cava to the left atrium. This produced chronic cyanosis with a mean pO2 of 48 +/- 4 mm Hg and polycythemia with a mean hematocrit of 56 +/- 2 gm%. Three to 5 months after preparation, these cyanotic dogs and five control dogs each received diatrizoate (a high osmolarity ionic agent) or ioversol (a low osmolarity nonionic agent), 465 mg iodine/kg body weight, by intravenous bolus injection. One month later, each animal received the other agent. The order of administration was randomized. Renal function studies, including serum creatinine and creatinine clearance, were performed precontrast, after 60 min, and 24 hr postcontrast. Neither agent adversely affected renal function in either the cyanotic or the normal group. We conclude that at the doses that are commonly used in clinical practice, high osmolarity ionic contrast agents do not create a greater risk of renal injury than do low osmolarity nonionic agents in this model of cyanosis.
    Catheterization and Cardiovascular Diagnosis 02/1994; 31(1):90-3.
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    ABSTRACT: Although the early mortality for repair of truncus arteriosus has decreased in the modern era, routine correction in the neonate has not been widely adopted. To assess the results of our protocol of early repair, we reviewed 46 neonates and infants undergoing repair of truncus arteriosus at the University of Michigan Medical Center from January 1986 to January 1992. Their ages ranged from 1 day to 7 months (median 13 days) and weights from 1.8 kg to 5.4 kg (mean 3.1 kg). Repair was performed beyond the first month of life in only 8 patients, because of late referral in 7 and severe noncardiac problems in 1. Associated cardiac anomalies were frequently encountered, the most common being interrupted aortic arch (n = 5), nonconfluent pulmonary arteries (n = 4), hypoplastic pulmonary arteries (n = 4), and major coronary artery anomalies (n = 3). Truncal valve replacement was performed in 5 patients with severe regurgitation, 3 of whom also had truncal valve systolic pressure gradients of 30 mm Hg or more. The truncal valve was replaced with a mechanical prosthesis in 2 patients and with a cryopreserved homograft in 3 patients. Right ventricle-pulmonary artery continuity was established with a homograft in 41 patients (range 8 mm to 15 mm), a valved heterograft conduit in 4 (range 12 mm to 14 mm), and a nonvalved polytetrafluoroethylene tube in the remaining patient (8 mm). There were 5 hospital deaths (11%, 70% confidence limits 7% to 17%). Multivariate and univariate analyses failed to demonstrate a relationship between hospital mortality and age, weight, or associated cardiac anomalies. Only 1 death occurred among 9 patients with interrupted aortic arch or nonconfluent pulmonary arteries. Hospital survivors were followed-up from 3 months to 6.3 years (mean 3 +/- 0.4 years). Late noncardiac deaths occurred in 3 patients, all within 4 months after the operation. Actuarial survival was 81% +/- 6% at 90 days and beyond. Despite the prevalence of major associated conditions, early repair has resulted in excellent survival. We continue to recommend repair promptly after presentation, optimally within the first month of life.
    Journal of Thoracic and Cardiovascular Surgery 07/1993; 105(6):1057-65; discussion 1065-6. · 3.53 Impact Factor
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    ABSTRACT: The bidirectional Glenn operation may be particularly useful as an intermediate procedure before Fontan correction in high-risk patients. From October 1989 through February 1992, 50 patients 1 to 60 months old (median 12) have undergone a bidirectional Glenn operation. Diagnoses included hypoplastic left heart syndrome in 21 patients, pulmonary atresia with intact ventricular septum in 10, tricuspid valve atresia in 9, other complex univentricular heart defects in 9, and Ebstein's anomaly in 1. Mean pulmonary vascular resistance was 2.2 +/- 0.2 Wood U (range 0.5 to 7.3) and mean pulmonary artery area Nakata index was 318 +/- mm2/m2 (range 80 to 821). Additional procedures were performed in 17 patients, including pulmonary artery reconstruction in 15 (29%) and bilateral caval anastomoses in 5 (10%). There were 4 hospital deaths (8%). Two deaths resulted from myocardial infarction in patients with pulmonary atresia with intact ventricular septum and sinusoids and 1 from severe pulmonary vascular disease in a patient with hypoplastic left heart syndrome. There was 1 late death from pneumonia. Actuarial survival is 92 +/- 4% at 1 month and beyond, with a mean follow-up of 13.4 +/- 1 months. Risk factor analysis showed that pulmonary vascular resistance >3 Wood U and pulmonary artery distortion were associated with increased mortality. Twelve patients have undergone a Fontan procedure at a mean duration after bidirectional Glenn of 18 months with 1 death (8%). The bidirectional Glenn procedure provides excellent palliation in high-risk patients and appears useful as a staging procedure before Fontan correction. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/30841/1/0000503.pdf
    The American Journal of Cardiology 04/1993; · 3.21 Impact Factor
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    ABSTRACT: Neonates with ventricular septal defect and aortic arch obstruction frequently have subaortic stenosis resulting from posterior deviation of the infundibular septum. Because the aortic anulus is often hypoplastic, making direct resection of the infundibular septum through the standard transaortic approach difficult, the optimal method of repair is uncertain. From September 1989 through November 1991, seven patients with ventricular septal defect, coarctation (n = 4), or interrupted aortic arch (n = 3) and severe subaortic stenosis underwent repair with use of a technique that included transatrial resection of the infundibular septum. Their ages ranged from 5 to 63 days (median 15 days) and weights from 1.3 to 5.4 kg (mean 3.1 kg). Only one patient was older than 1 month. The systolic and diastolic ratios of the diameter of the left ventricular outflow tract to that of the descending aorta were 0.53 +/- 0.09 mm (standard deviation) and 0.73 +/- 0.11, respectively. At operation, the posteriorly displaced infundibular septum was partially removed through a right atrial approach by resecting the superior margin of the ventricular septal defect up to the aortic anulus. The resulting enlarged ventricular septal defect was then closed with a patch to widen the subaortic area. In each patient the aortic arch was repaired by direct anastomosis. All patients survived operation; there was one late death from noncardiac causes 3 months after repair. The survivors remain well from 3 to 14 months after repair (mean 8 months). All are in sinus rhythm and none has a residual ventricular septal defect. One patient underwent successful balloon dilation of a residual aortic arch gradient late after repair. No patient has significant residual subaortic stenosis, although one has valvular aortic stenosis. This series suggests that in neonates with ventricular septal defect and severe subaortic stenosis resulting from posterior deviation of the infundibular septum, direct relief can be satisfactorily accomplished from a right atrial approach. This method provides effective widening of the left ventricular outflow tract and is superior to palliative techniques or conduit procedures.
    Journal of Thoracic and Cardiovascular Surgery 03/1993; 105(2):289-95; discussion 295-6. · 3.53 Impact Factor
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    ABSTRACT: Discrete subaortic stenosis typically appears as a well-defined membrane beneath the aortic valve. To assess the merits of alternative approaches to this problem, we have reviewed the results of operations for discrete subaortic stenosis from 1978 through 1990. Excision of the subaortic membrane alone was performed in 16 patients (group I). Excision of the membrane with resection of septal muscle was performed in 24 patients (group II). The groups were similar in age at operation, duration of follow-up, and preoperative and postoperative transvalvar gradients. There were no operative or late deaths. Reoperations for recurrent subaortic stenosis were performed in 4 group I patients (25%; 70% confidence limits, 16% to 38%) and 1 group II patient (4%; 70% confidence limits, 2% to 11%). Pacemakers were inserted for postoperative complete heart block in 1 group I patient (6%; 70% confidence limits, 2% to 16%) and 2 group II patients (8%; 70% confidence limits, 4% to 16%). We conclude that muscle resection combined with membrane excision in patients with discrete subaortic stenosis does not increase the risk of death or heart block, and does lower the risk of reoperation for recurrent subaortic stenosis.
    The Annals of Thoracic Surgery 10/1992; 54(3):467-70; discussion 470-1. · 3.45 Impact Factor
  • A K Pridjian, T A Tacy, D Teske, E L Bove
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    ABSTRACT: Failure to repair transposition of the great arteries and ventricular septal defect in the young infant results in the early development of pulmonary vascular occlusive disease. Complete repair, preferably by an arterial switch procedure and ventricular septal defect closure, may then not be possible. We report a palliative arterial switch procedure in a 5 1/2-year-old patient with transposition, ventricular septal defect, and severe pulmonary vascular obstructive disease in whom progressive hypoxemia and exercise intolerance developed. An arterial repair without ventricular septal defect closure was performed. After the operation, the child's systemic arterial oxygen saturation and exercise tolerance have substantially improved. Although the progression of pulmonary vascular disease may not be altered, arterial repair can provide effective palliation in this subset of patients.
    The Annals of Thoracic Surgery 09/1992; 54(2):355-6. · 3.45 Impact Factor
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    ABSTRACT: The optimal calcium concentration in cardioplegia for the newborn has not been determined. Therefore, the effect of 0, 0.6, 1.2, 1.8, and 2.4 mmol/L calcium in modified St. Thomas cardioplegia was evaluated in isolated working hearts of 7- to 10-day-old rabbits. Functional recovery was determined by comparing aortic flow, developed pressure, and first derivative of left ventricular pressure (dP/dt) before and after 1 hour of normothermic (37 degrees C) ischemia. As percentages of baseline values, recovery of developed pressure and dP/dt averaged 10% +/- 1% (mean +/- standard error of the mean) and 10% +/- 1% with 0 mmol/L, 46% +/- 7% and 44% +/- 8% with 0.6 mmol/L, 79% +/- 2% and 76% +/- 2% with 1.2 mmol/L, 67% +/- 2% and 61% +/- 5% with 1.8 mmol/L, and 65% +/- 5% and 65% +/- 7% with 2.4 mmol/L calcium, respectively. Significant improvement in recovery of developed pressure and dP/dt was detected when the calcium concentration was increased from 0 to 0.6 mmol/L and from 0.6 to 1.2 mmol/L, but the groups with 1.2, 1.8, and 2.4 mmol/L did not differ from one another significantly in terms of developed pressure and dP/dt recovery. There was no recovery of aortic flow when 0 mmol/L calcium was used; at calcium concentrations of 0.6, 1.2, 1.8, and 2.4 mmol/L, recovery of aortic flow averaged 16% +/- 7%, 63% +/- 10%, 23% +/- 10%, and 36% +/- 11% of baseline values, respectively. Recovery of aortic flow with 1.2 mmol/L calcium was significantly higher than at concentrations of 0.6 and 1.8 mmol/L.(ABSTRACT TRUNCATED AT 250 WORDS)
    The Annals of Thoracic Surgery 09/1990; 50(2):262-7. · 3.45 Impact Factor