Tracheal wire stent complications in malacia: implications of position and design.

BACKGROUND: Although expandable endoluminal wire stents that can be incorporated into body tissues are very attractive for use in the airway, disease-related factors that can lead to stent failure have received little attention in the literature. METHODS: The cases of all 4 patients who underwent insertion of one or more Gianturco stents into the trachea, main bronchi, or both for tracheobronchial malacia in our institution were reviewed. RESULTS: All three tracheal stents required removal for stent-related complications within the first 6 months. Complications included metallic strut fracture and unraveling or breakage of the encircling nylon suture leading to progressively bizarre and widening radiographic configurations suggesting imminent airway perforation. One of the six bronchial stents disrupted 10 months after insertion. CONCLUSIONS: Our findings suggest relatively less dynamic, repetitive bending wire stress in the bronchus (and likewise strictured trachea) compared with the malacic trachea. Although Gianturco stents are easily placed and give excellent functional results, we recommend against their use in the trachea for tracheal malacia. The bronchial position may be reasonably safe.

Relation between graded, subcritical impairments of coronary flow reserve and regional myocardial dysfunction induced by isoproterenol infusion in dogs.

Isoproterenol has been used experimentally and clinically to elicit ischemia. The usefulness of this approach, however, in eliciting regional dysfunction in the presence of mild to moderate single-vessel coronary disease quantitated on the basis of coronary flow reserve measurements has not been previously defined. Open-chest, anesthetized dogs were instrumented with an electromagnetic flow probe, high-fidelity micromanometers, and subendocardial ultrasonic crystals. A rigid, screw occluder was used to produce five subcritical coronary stenoses in each dog associated with varying impairment of postocclusion reactive hyperemia at rest but no impairment of resting coronary blood flow. Regional function at rest and in response to the isoproterenol challenge (0.25 micrograms/kg/min) in nonstenotic and stenotic conditions was assessed. Relative regional function was maintained during the infusion until nearly total loss of coronary flow reserve. With this near-critical stenosis, function was lower than in the nonstenotic state but remained greater than resting control values. Moderate impairments of coronary flow reserve were not associated with isoproterenol-induced deterioration of regional function. In conclusion, detection of impaired coronary flow reserve at rest is a more sensitive index of the severity of a coronary stenosis than is detection of regional dysfunction during isoproterenol challenge. Failure to maintain the expected isoproterenol-induced increase in regional function is manifested only when stenoses are associated with nearly total loss of resting coronary flow reserve. This suggests that the clinical use of isoproterenol challenge is not effective in eliciting regional dysfunction when mild coronary disease is present.

The hemodynamic determinants of the isovolumic index.

The isovolumic index is a recently described echocardiographic parameter of left ventricular function that is calculated as the ratio between the sum of the time of isovolumic contraction and relaxation divided by the ejection time. Although the individual components of this index may be altered by heart rate and loading conditions, an analysis of the net effect of such alterations on the isovolumic index has not been undertaken. Thus, dogs were instrumented with high-fidelity micromanometers in the left ventricle, ascending aorta, and left atrium to allow determination of the individual components of the isovolumic index and calculation of the index itself. Four sets of experiments were undertaken in random order. Left atrial pacing was used to increase heart rate by approximately 10 bpm in five steps. Preload was elevated in five stages by saline infusions which caused successive increases of 1 to 2 mm Hg in the left ventricular end-diastolic pressure. Systolic blood pressure was lowered or raised by approximately 10 mm Hg per stage by three progressive, steady-state infusions of nitroprusside and phenylephrine, respectively. These experiments demonstrated little change in the isovolumic index over a broad range of heart rate. Increased left ventricular end-diastolic pressure and decreased systemic pressure caused shortening of the index. Multiple regression analysis of all experiments yielded the following: isovolumic index = 0.41 - 0.015 (left ventricular end-diastolic pressure) + 0.004 (systolic blood pressure); r = 0.57, standard error = 0.13, p less than 0.0001. Therefore, this investigation establishes the hemodynamic determinants of the isovolumic index and provides the basis for interpretation of directional changes in response to cardiac diseases and cardioactive drugs that can alter loading conditions.

Expandable metallic esophageal stents in benign disease: a cause for concern.

Over a 2-year period at our institution, 6 patients underwent metallic stent treatment, 5 for malignant conditions and 1 for a benign condition of the esophagus. The use of expandable metallic stents for benign strictures has paralleled malignant indications but is limited and less understood from a clinical standpoint. A review of current literature in the treatment of benign strictures is presented. Treatment of benign strictures is associated with high morbidity and mortality as demonstrated by the cumulative experience of 21 patients. Migration, hyperplastic tissue obstruction at the terminal ends, reflux, and complications of perforation occur at a prohibitive rate. We conclude that expandable metallic stents should be reserved for palliative treatment of esophageal malignant obstructions and tracheoesophageal fistulas. Pharmacological management, necessary dilatations and operative corrections (antireflux procedures, esophagectomy) are recommended treatments for benign strictures.