Presence Of Outflow Tract Obstruction Research Articles

Impact of outflow tract obstruction in the management of atrial fibrillation in hypertrophic cardiomyopathy: insights from the national readmission database

Abstract Background Atrial fibrillation (AF) is commonly encountered in patients with Hypertrophic Cardiomyopathy (HCM). Presence of AF in this high risk population is detrimental due to its effect on hemodynamics, diastolic function and potential induction of ventricular tachyarrhythmias. For these reasons a rhythm control strategy is highly desirable, and yet catheter ablation of AF is consistently inefficacious with poorer overall outcomes. We hypothesize that in HCM presence of outflow tract obstruction by virtue of its effect on left atrial hemodynamics, altered circulatory flow patterns in the pulmonary veins, and stretch related triggered activities would create an arrhythmogenic substrate, and have significant impact on the outcomes of catheter ablation of AF. In this study, we aimed to evaluate AF ablation outcomes based on the presence or absence of outflow tract obstructions in patients with HCM. Methods We conducted a retrospective study using the AHRQ-HCUP National Readmission Database for the years 2016–17. All adults (≥18 years) with HCM undergoing AF ablation procedures were identified using ICD-9 codes. The cohort was divided into two groups; Obstructive HCM (Group A) and Non-Obstructive HCM (Group B) Multivariate regression analysis was utilized to adjust for confounders. Independent risk factors for in-hospital mortality were identified using a proportional hazards model. Complications were defined as per the Agency for Health Care Research and Quality guideline. Results From a total of 71,451,419 patients in the NRD registry, 97 patients with HCM were identified and formed the study cohort. When divided based on the presence or absence of outflow tract obstruction, there were 25 patients with Obstructive HCM and 72 patients with Non-obstructive HCM. Both groups were similar in clinical characteristics including CHADVASc scores and Charlson Comobidity indices as outlined in Table 1. Procedural outcome analysis revealed higher 30-day cardiac readmissions in the Obstructive HCM group compared to Non-obstructive HCM (25.2% vs 7.97%, p=0.049). The Obstructive HCM group had higher rates of atrial arrhythmias, 57.97%, compared to 32.44% in the non-obstructive HCM group, and heart failure exacerbations, 41.27% vs 25.82%. However, both indices did not reach statistical significance. The procedural complications rates tended to be higher in the non-obstructive HCM group, 10.8% vs. 5.6% in the Obstructive HCM group (p=0.54). Conclusions Presence of an obstructive component to HCM is associated with significantly increased short term cardiac readmissions predominantly driven by recurrent atrial arrhythmias and heart failure. These findings suggest negative influence of altered cardiac hemodynamics related to outflow tract obstruction on atrial arrhythmias. The arrhythmogenic substrate of HCM may therefore be different and less amenable to catheter ablation. HCM ablation outcomes Funding Acknowledgement Type of funding source: None

Fetal Cardiac Rhabdomyoma: A Case Report

Background: Fetal cardiac rhabdomyoma is a rare condition. Case: We report a case with cardiac mass discovered in utero by prenatal ultrasonography at 33 weeks of gestational age. An echogenic round-oval shape mass at the interventricular septum protrudes to left ventricle was observed. Results: After birth, the baby was followed up for 7 months with echocardiography, physical examination, and computerized tomography scan, to rule out anything related to tuberous sclerosis. The prognosis depends on the size, site, number of tumors, and co-existing congenital abnormalities. Management highly depends on the presence of outflow tract obstruction of the heart. However, some cases may regress after birth.Â

Comparison of Long-Term Outcome between Apical and Asymmetric Septal Hypertrophic Cardiomyopathy

Objectives: As reported, diagnostic age, gender and presence of outflow tract obstruction have an impact on prognosis in patients with hypertrophic cardiomyopathy. The aim of this study was to compare the long-term outcome between apical hypertrophic cardiomyopathy (ApHCM) and asymmetric septal hypertrophic cardiomyopathy (ASHCM) after the exclusion of these factors. Methods: A total of 540 patients (270 with ApHCM and 270 with ASHCM) identified in a consecutive single-center cohort were retrospectively studied. The two groups were matched by diagnostic age, gender and the presence of outflow tract obstruction. Clinical characteristics and long-term outcomes were compared. Results: The mean follow-up duration in ASHCM and ApHCM were 6.6 ± 5.5 and 7.6 ± 4.1 years, respectively. During follow-up, 16 patients experienced cardiovascular death in the ASHCM group, while 2 patients experienced cardiovascular death in the ApHCM group (6.3 vs. 0.7%, p < 0.01). Cardiovascular morbidity in the ASHCM and ApHCM groups were 39.9 and 18.5% (p < 0.01). In the multivariate Cox regression analysis late gadolinium enhancement (LGE; HR 4.81, 95% CI 1.28-78.0, p = 0.03) and unexplained syncope (HR 9.68, 95% CI 1.9-17.2, p < 0.01) were independent predictors for cardiovascular mortality. Unexplained syncope was independently associated with a higher risk for sudden cardiac death (HR 4.3, 95% CI 1.2-15.3, p = 0.02). Conclusions: After eliminating the interference of diagnostic age, gender and outflow tract obstruction, ASHCM represented a worse prognosis with a higher incidence of cardiovascular mortality and morbidity than ApHCM. LGE was a strong predictor for cardiovascular death.

Effect of Bladder Outflow Obstruction on the Innervation of the Rabbit Urinary Bladder

The effects of bladder outflow obstruction on the innervation of the bladder were studied using a rabbit animal model. Partial occlusion of the bladder neck was obtained by the placement of a silk ligature at that level; control animals underwent a sham procedure. After a 3-month period, the presence of outflow tract obstruction was confirmed using urodynamic studies. The animals were then killed and pharmacological assessments of the bladder innervation undertaken. Detrusor muscle strip studies provided evidence of damage to the cholinergic innervation of the detrusor. Also, muscle strips from obstructed animals showed reduced inhibitory responses to beta-adrenergic stimulation with isoprenaline. In addition to these muscle strip studies, the bladder content of the neuropeptide substance P was assayed, but no significant change was observed in response to obstruction. This finding suggests that substance P-containing sensory nerves may be spared from the denervating effect of bladder outflow obstruction.

Estimating Relative Renal Function

Radionuclide measurements of relative renal function have been made using conventional dual-probe renography, computer assisted triple-probe renography, rectilinear kidney scanning and computer assisted gamma camera renography and kidney scanning. The relative area of each kidney from the excretory urogram also has been used to measure relative function.The best correlation between renography and kidney scanning was obtained with the gamma camera computer system. The relative function of each kidney was obtained by outlining regions of interest that corresponded closely to the renal images and subtracting the blood and tissue background activity, using a special background region.Triple-probe renography, using computer assisted blood background subtraction, provides another reliable indicator of relative function, which is considerably more accurate than conventional dual-probe renography.Relative renal function also may be determined, but with less precision, from the relative counts in a rectilinear kidney scan, from the relative scan areas and from the relative areas found on excretory urography. Both relative area methods are less reliable in the presence of outflow tract obstruction, renal tumors and renal cysts.