A rare case of acquired aortopulmonary fistula with bicuspid aortic valve: report of successful surgical repair

An Unusual Case of an Acquired Aortopulmonary Fistula after Surgical Replacement of a Bicuspid Aortic Valve

Aortopulmonary fistulas are extremely rare and often occur as a result of long-standing aortic aneurysms. They are most frequently due to the erosion of a false aneurysm of the ascending or descending thoracic aorta into the pulmonary artery. Patients generally present with symptoms of acute decompensated heart failure due to a sudden formation of a left-to-right shunt. Here, we present the case of a 63-year-old male who acquired an aortopulmonary fistula four months after undergoing successful bioprosthetic aortic valve replacement.

Short trains of transcutaneous auricular vagus nerve stimulation (taVNS) have parameter-specific effects on heart rate

BACKGROUND

Optimal parameters of transcutaneous auricular vagus nerve stimulation (taVNS) are still undetermined. Given the vagus nerve's role in regulating heart rate (HR), it is important to determine safety and HR effects of various taVNS parameters.

OBJECTIVE

We conducted two sequential trials to systematically test the effects of various taVNS parameters on HR.

METHODS

15 healthy individuals participated in the initial two-visit, crossover exploratory trial, receiving either tragus (active) or earlobe (control) stimulation each visit. Nine stimulation blocks of varying parameters (pulse width: 100 μs, 200 μs, 500 μs; frequency: 1 Hz, 10 Hz, 25 Hz) were administered each visit. HR was recorded and analyzed for stimulation-induced changes. Using similar methods and the two best parameters from trial 1 (500μs 10 Hz and 500μs 25 Hz), 20 healthy individuals then participated in a follow-up confirmatory study.

RESULTS

Trial 1- There was no overall effect of the nine conditions on HR during stimulation. However multivariate analysis revealed two parameters that significantly decreased HR during active stimulation compared to control (500μs 10 Hz and 500μs 25 Hz; p < 0.01). Additionally, active taVNS significantly attenuated overall sympathetic HR rebound (post-stimulation) compared to control (p < 0.001). Trial 2-For these two conditions, active taVNS significantly decreased HR compared to control (p = 0.02), with the strongest effects at 500μs 10 Hz (p = 0.032).

CONCLUSION

These studies suggest that 60s blocks of tragus stimulation are safe, and some specific parameters modulate HR. Of the nine parameters studied, 500μs 10 Hz induced the greatest HR effects.