The aortic uncrossing procedure

OBJECTIVE

Cross-sectional imaging allows identification of rare patients with a vascular ring and circumflex aorta. The key diagnostic feature is crossing of the transverse aortic arch from right to left posterior to the trachea and superior to the carina in a patient with a right aortic arch. We evaluated our patients who received an aortic uncrossing procedure.

METHODS

We reviewed all patients who underwent aortic uncrossing from 2002 to 2022. All patients received preoperative computed tomography imaging and bronchoscopy.

RESULTS

Eleven patients ranging in age from 1.5 to 10 years (median 4 years) underwent aortic uncrossing. Two patients had prior left ligamentum division, and 3 patients had prior left aortic arch division. All had significant clinical symptoms. Eight patients had deep hypothermic circulatory arrest (mean 34 minutes), and 3 patients had antegrade cerebral perfusion (median, 28 minutes). Patch material was not used for aortic augmentation, and no patient underwent a posterior tracheopexy or rotational esophagoplasty. Postoperative length of stay ranged from 4 to 31 days (median, 5 days). One patient required a temporary tracheostomy for bilateral recurrent laryngeal nerve paresis, which recovered. One patient required an aortic extension graft to alleviate esophageal compression from an unusual ectatic esophageal course. All patients had relief of airway symptoms and dysphagia.

CONCLUSIONS

In properly selected patients with a right aortic arch and circumflex aorta, aortic uncrossing is a safe and effective therapy to treat airway and esophageal compression. The procedure can be conducted with deep hypothermic circulatory arrest or antegrade cerebral perfusion. Careful attention to the location of the esophagus and recurrent laryngeal nerves is required.

Lower liver transplant success in females: gender differences in metabolic response to global ischemia

BACKGROUND

Research has shown that gender plays a significant role in the metabolic processes of different organs and that transplanting livers of females into male or female recipients has significantly higher failure rates. To understand why, this study examined whether gender differences exist in various metabolic responses of livers to ischemia.

METHODS

The following metabolic liver parameters in Sprague-Dawley rats (male, n = 14; and female, n = 18) were examined; adenosine triphosphate (ATP) and lactate expressed as micromoles/g dry weight, and hydrogen ion content [H+] expressed as 10(-8) mol/L. In vivo liver biopsy specimens were compared with ischemic biopsy specimens at 3, 10, 15, 30, and 45 minutes (37 degrees C).

RESULTS

In vivo female ATP values (9.9 +/- 0.8) were similar to males (9.8 +/- 0.9) and both had early, rapid decline during ischemia reaching 20% of baseline by 10 minutes of ischemia. In contrast, male liver lactate accumulation peaked by 3 minutes and at much lower levels (35 +/- 13), whereas female liver lactate peaked by 10 minutes at 71 +/- 11. For the rest of the ischemic period, female livers exhibited significantly (P < .05) greater lactate accumulation. Female liver H+ levels also increased to higher levels (55 +/- 10) than the male livers (37 +/- 7) and this pattern was significantly (P < .05) different from 10 minutes onward.

CONCLUSIONS

Although livers of females ultimately have similar ATP profiles to livers of males, they experienced more rapid and greater degree of tissue lactate and H+ accumulation during ischemia. Therefore, female livers have increased acidosis during ischemia, which could adversely affect transplant outcome.

A long-term stable normothermic cardiopulmonary bypass model in neonatal swine

BACKGROUND

An appropriate animal model of cardiopulmonary bypass (CPB) is critical in order to study the morbidity and mortality in newborn children undergoing long-term cardiac surgery. Since this has been reported to be technically difficult, this paper describes a neonatal porcine CPB model (3 days old, n = 18) for up to 8 h to study long-term bypass.

METHODS

After anesthesia, neonates had arterial/venous monitoring lines inserted, they were heparinized (300 IU/kg), the aorta was cannulated for arterial retroperfusion, and a two-stage venous drainage catheter was placed in the right atrium. A Medtronic Minimax Plus oxygenator and the bypass circuit were primed with donor blood and CPB was instituted.

RESULTS

Line and mean arterial pressures were kept at 147.7 +/- 73 and 62.7 +/- 9 mm Hg, respectively. Myocardial (38.1 +/- 1.0 degrees C) and rectal temperatures (37.7 +/- 1.0 degrees C) were maintained. Heart rate was 184.8 +/- 34.5 bpm. Hematocrits were 29.6 +/- 6.0%, activated clotting time was sustained above 400 s throughout bypass, blood gas parameters were maintained in the normal range (pH, 7.39 +/- 0.1; PO(2), 123.1 +/- 65.2 mm Hg; PCO(2), 37.2 +/- 8.5 mm Hg; and HCO(3)(-), 21.5 +/- 3.6 mmol/L). CPB was terminated after 8 h and no visceral edema or other imbalances normally associated with swine on bypass were observed.

CONCLUSIONS

Results demonstrate a model of stable long-term bypass in neonatal swine which can be used to study issues critical to children requiring surgical correction and CPB at a young age. Overall effects of surgery and bypass on these younger patients have yet to be explored and therefore a stable long-term normothermic model of CPB would allow the study of numerous parameters associated with this complicated procedure.

Sex hormones and the selective estrogen receptor modulator tamoxifen modulate weekly body weights and food intakes in adolescent and adult rats

This study documented the effect of changes in male and female sex hormones and the selective estrogen receptor modulator (SERM) tamoxifen on weight gain and food consumption of rats from puberty to adulthood, and assessed whether age at onset of treatment affected outcome. In Study 1, male and female WKY rats were either neutered or sham-operated before puberty, and a subgroup of neutered females underwent estrogen replacement (ERT) at the age of puberty. In Study 2, subgroups of neutered females received either ERT or tamoxifen beginning well into the postpuberty period. Weekly body weight and food consumption were assessed, and food consumption was normalized to metabolic weight (body weight(0.67)). Neutering reduced the rate of weight gain in males (P < 0.05), but significantly increased it in females (P < 0.0001). ERT immediately reduced weight gain and prevented any further increase, resulting in weights below that of sham-operated females (P < 0.05). Tamoxifen prevented further weight gain and returned profiles to that of sham-operated females. Food consumption, normalized to metabolic weight, was similar in females and males, and both sexes showed a decrease through maturation to adulthood. Neutering decreased food consumption below that of sham-operated animals in both males and females (P < 0.05), and ERT returned it to sham levels. Despite the fact that tamoxifen had an effect on body weight similar to that of ERT, females receiving tamoxifen treatment consumed less food than both sham-operated and ERT females (P < 0.05). Weight gain is modulated by sex hormones in male and female rats, with both estrogen and tamoxifen exerting immediate effects in females, irrespective of the age at which treatment is initiated. Differences in food consumption do not appear to account for the effects of hormones and tamoxifen on body weight, suggesting that they exert a direct effect on overall body metabolism.

Gender-differences in myocardial adaptation to afterload in normotensive and hypertensive rats

Echocardiographic studies suggest that women appear to exhibit a greater degree of myocardial hypertrophy in response to increased afterload than men. Therefore, gender differences and the role of estrogen and testosterone in the development of myocardial hypertrophy were studied in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. Male and female rats were either surgically neutered or underwent a sham operation at 21 days of age. A subgroup of neutered females of each strain received 17beta-estradiol replacement. At 6 months, the heart weight-to-body weight ratio was assessed and correlated with systemic blood pressure. Compared with males, females had significantly smaller body and heart weights in both normotensive and hypertensive strains. Despite this, females consistently had significantly greater heart weight-to-body weight ratios. In females, neutering significantly lowered the heart weight-to-body weight ratio in WKY rats, which was returned to intact levels with estrogen replacement. Female SHR showed similar, but not statistically significant, responses. In males, neutering appeared to result in a higher heart weight-to-body weight ratio in WKY rats, but the opposite was seen in SHR. In addition, there was a significant correlation between arterial blood pressure and heart weight-to-body weight ratio (systolic r=0.45, P=0.0015: diastolic r=0.52, P=0.0002) in intact males and females of both strains, and for a given diastolic pressure, females always exhibited a greater heart weight-to-body weight ratio than males. Thus, a greater degree of myocardial hypertrophy in females appears to be related to the presence of estrogen in both normotensive and hypertensive rats. Females show a stronger relationship between heart/body weight and blood pressure than males, which occurred independent of the presence of estrogen.

Metabolic and functional response of neonatal pig hearts to the development of ischemic contracture: is recovery possible?

The potential for functional and metabolic recovery in neonatal hearts after the development of ischemic contracture remains controversial and undefined. This study documents post-ischemic recovery of metabolism and function in the in vivo neonatal heart after the development of onset and peak ischemic contracture. In piglets on cardiopulmonary bypass, hearts were reperfused after the development of either onset (TICo) or peak (TICp) ischemic contracture. Systolic (developed and systolic function, contractility) and diastolic (diastolic function, relaxation) performance was assessed throughout reperfusion. Biopsies were obtained at end-ischemia or end-reperfusion to assess metabolism. By end-ischemia, the metabolic profiles of both TICo and TICp hearts confirmed energy-store depletion and purine degradation that was quantitatively greater in TICp hearts. Hearts reperfused at TICo had consistent moderate impairment of developed function, contractility, diastolic function, and relaxation, whereas hearts reperfused at TICp had much more profound functional impairment. Diastolic function showed the worst functional recovery. In contrast, systolic function was not significantly altered in either study group and, thus, did not reflect the actual extent of injury. In addition, TICo hearts either did not further deplete or partially regenerated energy stores during reperfusion, whereas TICp hearts had further energy-store depletion and lactate accumulation. In summary, neonatal hearts reperfused after TICo maintained or partially restored energy stores and had significant but incomplete functional recovery. In contrast, further metabolic deterioration and profound functional impairment occurred with reperfusion after TICp, potentially indicating ongoing mitochondrial injury and compromised oxidative phosphorylation.

Does the degree of cyanosis affect myocardial adenosine triphosphate levels and function in children undergoing surgical procedures for congenital heart disease?

OBJECTIVE

The outcome of children with cyanosis after cardiac surgical procedures is inferior to that of children who are acyanotic. Animal studies indicated detrimental effects of chronic hypoxia on myocardial metabolism and function. We studied whether the presence or the degree of cyanosis adversely affected myocardial adenosine triphosphate, ventricular function, and clinical outcome in children.

METHODS

Forty-eight children who underwent repair of tetralogy of Fallot were divided according to their preoperative saturation: group I, 90% to 100% (n = 14 patients); group II, 80% to 89% (n = 16 patients); and group III, 65% to 79% (n = 18 patients). Adenosine triphosphate was measured from right ventricular biopsy specimens taken before ischemia, at 15 minutes of ischemia, at end-ischemia, and at 15 minutes of reperfusion. Ejection fraction was measured by echocardiography.

RESULTS

Even before surgical ischemia, compared with groups I and II, group III had lower preoperative ejection fraction (59% +/- 2.9% vs 67% +/- 1.7% and 68% +/- 1.0%; P <.01) and lower preischemic adenosine triphosphate levels (15.1 +/- 2.1 vs 19.1 +/- 1.9 and 21.4 +/- 1.5 micromol/g dry weight; P <.01). After 15 minutes of ischemia, group III had lower adenosine triphosphate levels (11.2 +/- 1.8 vs 14.77 +/- 2.3 and 17. 6 +/- 3.1 micromol/g dry weight; P <.01). With reperfusion, both cyanotic groups lost further adenosine triphosphate compared with partial recovery in the acyanotic group (-22% +/- 3.8%, -20% +/- 3. 1% vs +18% +/- 1.8%; P <.01). Children in group III had a more complicated postoperative course as evidenced by longer ventilatory support (85 +/- 25 hours vs 31 +/- 15 and 40 +/- 21 hours; P =.07), inotropic support (86 +/- 23 hours vs 38 +/- 12 and 36 +/- 4 hours; P <.01), and intensive care unit stay (160 +/- 35 hours vs 60 +/- 10 and 82 +/- 18 hours; P =.02).

CONCLUSIONS

The degree of cyanosis adversely affects myocardial adenosine triphosphate, function, and clinical outcome of children who undergo cardiac operation. Children with cyanosis should be identified as a higher risk group that could be targeted for supportive interventions.

Extracellular calcium concentration affects susceptibility to global ischemic injury in newborn but not adult hearts

BACKGROUND

Whether immaturity in calcium handling, that persists for a time after birth, could increase sensitivity to extracellular calcium and affect the development of global ischemic injury in the newborn heart is unknown. To address this, the impact of alterations in extracellular calcium concentration on newborn vs. adult development of myocardial injury due to ischemia was studied.

METHODS

In Study 1, hearts of 3-day-old piglets and adult pigs were perfused with 1 of 3 different calcium concentrations: control (0.13 mmol/L); intermediate (2.23 mmol/L); high (4.44 mmol/L) before normothermic ischemia. In Study 2, newborn hearts were allocated to perfusion with or without the L-calcium channel antagonist verapamil before high (4.44 mmol/L) calcium exposure, followed by normothermic ischemia. Tolerance to ischemia was assessed by determining the time to irreversible injury in all hearts, and maximal intraventricular pressures at peak injury.

RESULTS

In adults, altering calcium did not significantly affect tolerance to ischemia. In newborns, increasing calcium exposure resulted in significantly greater intraventricular pressures at maximal injury when compared with the control (low) calcium group (p<.05). As well, newborns exposed to high calcium had a significantly shorter time to the development of ischemic injury compared with the other groups (p<.05). Those newborn hearts pretreated with an L-calcium channel antagonist before the high calcium exposure did not exhibit this increased susceptibility to ischemic injury (p<.05).

CONCLUSIONS

In contrast to adults, the development of ischemic injury in the newborn heart is affected by changes in extracellular calcium, that can be modified with an L-calcium channel antagonist. This information could be used to prolong the safe preservation time of newborn donor hearts harvested for transplantation, as well as to minimize postoperative ventricular dysfunction.

Sex differences in response to dietary manipulation in rats with hypertension and myocardial hypertrophy

Studies of the effect of sex on the metabolic state of rats with chronic hypertension and concomitant myocardial hypertrophy were conducted. Female and male spontaneously hypertensive rats (SHRs) with early myocardial hypertrophy (5.5 mo old) were used. Serum fatty acids, liver glycogen, and myocardial glycogen were measured at baseline and after the rats were deprived of food for 24 h. The metabolic effects of progressive myocardial hypertrophy in females were assessed in additional groups of female SHRs (5.5 or 12 mo old) under the following conditions: control, food deprived, or food deprived and refed with equienergetic lipid-rich (38.9% of total energy) or carbohydrate-rich (76.5% of total energy) diets. Despite no differences in serum fatty acids, females had significantly higher baseline myocardial glycogen and liver glycogen concentrations than males. In response to food deprivation, females continued to have significantly higher myocardial glycogen and fatty acid concentrations than males, whereas there were no sex differences in liver glycogen, which was depleted in both males and females. Older hypertensive females had higher baseline fatty acid concentrations and lower liver glycogen concentrations than younger females, whereas there were no differences in myocardial glycogen. Food deprivation doubled fatty acid concentrations, depleted liver glycogen, and increased myocardial glycogen in both age groups. In both age groups, fatty acid concentrations and liver glycogen did not return to baseline values after food deprivation and refeeding. In both age groups, fatty acid concentrations increased further after the lipid-rich diet whereas liver glycogen concentrations returned to approximately 50% of baseline values after the carbohydrate-rich diet. Refeeding with either diet did not significantly increase myocardial glycogen further. Thus, the metabolic response to dietary manipulation was influenced by both sex and, in females, progressive pathology.