Publications

OBJECTIVE

Laminar flow becomes disturbed at high velocities, reducing shear stress and augmenting vascular inflammation and proliferation, processes that are pivotal in restenosis and atherogenesis. We hypothesized that disturbed blood flow after coronary angioplasty is associated with adverse long-term clinical outcome.

METHODS AND RESULTS

The cineangiograms from 97 patients undergoing laser-assisted coronary angioplasty were analyzed. Coronary blood flow velocity, the residual lesion dimensions, and the Reynolds number (an index of disturbed flow) were measured by using a frame-counting technique and quantitative coronary angiography. Cox proportional hazards were used to assess the relative risk of adverse events (target-vessel revascularization, myocardial infarction, or death) over a mean 2.5 years after the index procedure. There were 41 adverse events during 245 patient years of follow-up (17% per year of follow-up). The risk of an adverse event was increased for patients with a high flow velocity (>250 mm/s; relative risk 2.5, 95% CI 1.3 to 4.7) or a high Reynolds number (>200) at the stenosis inlet (relative risk 2.1, 95% CI 1.1 to 4.1) at the end of the procedure. Adjustment for other factors did not alter these results.

CONCLUSIONS

High Reynolds numbers, indicating disturbed blood flow after coronary angioplasty, increase the risk of adverse clinical events, potentially through shear-stress-related molecular mechanisms that promote restenosis and atherogenesis.

The contribution of endothelin to resting pulmonary vascular tone and hypoxic pulmonary vasoconstriction in humans is unknown. We studied the hemodynamic effects of BQ-123, an endothelin type A receptor antagonist, on healthy volunteers exposed to normoxia and hypoxia. Hemodynamics were measured at room air and after 15 min of exposure to hypoxia (arterial PO(2) 99.8 +/- 1.8 and 49.4 +/- 0.4 mmHg, respectively). Measurements were then repeated in the presence of BQ-123. BQ-123 decreased pulmonary vascular resistance (PVR) 26% and systemic vascular resistance (SVR) 21%, whereas it increased cardiac output (CO) 22% (all P < 0.05). Hypoxia raised CO 28% and PVR 95%, whereas it reduced SVR 23% (all P < 0.01). During BQ-123 infusion, hypoxia increased CO 29% and PVR 97% and decreased SVR 22% (all P < 0.01). The pulmonary vasoconstrictive response to hypoxia was similar in the absence and presence of BQ-123 [P = not significant (NS)]. In vehicle-treated control subjects, hypoxic pulmonary vasoconstriction did not change with repeated exposure to hypoxia (P = NS). Endothelin contributes to basal pulmonary and systemic vascular tone during normoxia, but does not mediate the additional pulmonary vasoconstriction induced by acute hypoxia.

BACKGROUND

Pediatric tracheal procedures are uncommon. We reviewed our experience to clarify management and results.

METHODS

Retrospective single-institution review of pediatric tracheal operations, 1978 to 2001.

RESULTS

One hundred sixteen children were evaluated, mean age 10.4 years (10 days to 18 years). Tracheal pathology was postintubation stenosis (n = 72; 62%), congenital stenosis (n = 23; 20%), neoplasm (n = 8; 7%), tracheomalacia (n = 7; 6%), and trauma (n = 6; 5%). Twenty-nine patients had previous tracheal operations. Thirty-six patients received only a minor procedure. Eighty patients had major operations: tracheal resection (n = 46; 58%), laryngotracheal resection (n = 22; 28%), slide tracheoplasty (n = 7; 9%), and carinal resection (n = 5; 6%). The mean length of airway resected was 3.3 cm (1.5 to 6 cm), which represented 30% of the entire trachea. Twenty-eight patients (35%) had complications. These included tracheomalacia (n = 3), recurrent nerve injury (n = 3), laryngeal edema requiring intubation (n = 2), stroke (n = 1), esophageal leak (n = 1), and lobar collapse (n = 1). Nineteen patients had anastomotic failure: severe restenosis (n = 6), mild restenosis (n = 9), dehiscence (n = 2), dehiscence with tracheoesophageal fistula (n = 1), and tracheoinnominate fistula (n = 1). Two children died (2.5%). Complications were more frequent in children less than 7 years of age (p = 0.05) and after previous operations (p = 0.02). Longer fractions of tracheal resection (> 30%) were more likely to result in anastomotic failure (p = 0.0005). Sixty-four (80%) patients achieved a stable airway free of any airway appliance. All patients with neoplasms are alive.

CONCLUSIONS

The principles of adult tracheal operations are directly applicable to children and usually lead to a stable, satisfactory airway. Children tolerate anastomotic tension less well than adults; resections more than 30% have a substantial failure rate.