The Sinus Venosus Veno-Venous Bridge: Not a septal defect

This review provides an update on the morphology of the sinus venosus defect. It was earlier believed that a 'common wall' separated the right pulmonary veins from the superior caval vein. In the sinus venosus defects, this wall was absent. Current evidence shows that the superior rim of the oval fossa, rather than forming a second septum or representing a common wall, is an infolding between the walls of the caval veins and the right pulmonary veins. The sinus venosus defect is caused by the anomalous connection of one or more pulmonary veins to a systemic vein. However, the pulmonary vein(s) retain their left atrial connections, leading to a veno-venous bridge that allows interatrial shunting outside the oval fossa. True atrial septal defects are located within the oval fossa or in the anteo-inferior buttress, while sinus venosus defects, ostium defects and coronary sinus defects are morphologically distinct from them. Keywords: Heart Septal Defects, Atrial; Diagnostic Imaging; Sinoatrial Node; Vena Cava, Superior

Pulmonary Annulus Growth Pattern in Patients with Tetralogy of Fallot Prior to Surgical Repair

Objectives: The size of the pulmonary valve annulus often determines the feasibility of pulmonary valve preservation at the time of intracardiac repair of Tetralogy of Fallot. Currently, there is limited available data regarding the growth pattern and the determining factors that contribute towards pulmonary valve annulus growth. Methods: This retrospective study included patients who underwent surgical repair of Tetralogy of Fallot with or without prior palliation. These patients had an echocardiogram at the time of initial diagnosis and a second echocardiogram prior to intracardiac repair. The sizes of the pulmonary annulus, the right and left pulmonary arteries with z-scores were recorded. Patients with improvement in the pulmonary annulus z-scores between the 2 echocardiographic examinations were allocated in Group I (n = 46) and Group II (n = 68) were those with no improvement. Results: A total of 114 patients were included in the study. The right and left pulmonary arteries size and z scores improved significantly between the 2 echocardiograms. Although the median size of the pulmonary annulus increased between the 2 echocardiograms (6 and 7.9 mm; P<0.001), there was no significant change in the z-score (-2.2, -2.34; P = 0.185). Multivariate logistic regression analysis showed that gender, blood group, presence of collaterals, and palliation with Blalock-Taussig shunt had no impact on the improvement in pulmonary annulus z-score. Conclusion: In Tetralogy of Fallot, the pulmonary valve annulus z-score may not change significantly prior to the intracardiac repair. Although in certain subgroups there may be an improvement, there was no specific factor that could be identified and had an influence on this improvement. Keywords: Tetralogy of Fallot; Pulmonary Valve; Pulmonary Artery; Modified Blalock-Taussig Shunt; Oman

A Newly Detected Left Ventricular Mass Following A Complex Intracardiac Repair

Appearance of unexpected masses in the chambers of the heart during cardiac surgery can be intriguing. We report the case of a mass in the left ventricle that appeared at the time of separation from cardiopulmonary bypass in a child after a complex intracardiac repair. The child presented for surgery to a tertiary care hospital in Muscat, Oman, in 2022. Prior to the surgical repair the mass was not appreciated by echocardiography. An intraventricular baffle was used to divert left ventricular blood flow towards the outflow tract, after which an intraventricular “mass” was observed. Intraoperative transoesophageal echocardiography identified the mass as a portion of the interventricular septum that was located between the inlet and outlet ventricular septal defects. Keywords: Echocardiography; Heart Septal Defects; Heart Ventricles; Diagnostic Imaging

Sudden Cardiac Death in Patients Under 49 Years Including Adolescents: A single-centre study from Oman

Objectives: This study aimed to identify the incidence of sudden cardiac death (SCD0 in adult patients under the age of 49 years, including adolescents with an out-of-hospital cardiac arrest that presented to the emergency department of a tertiary care hospital. Methods: This retrospective cross-sectional study was conducted at the Royal Hospital, Muscat, Oman, between January 2015 and December 2019. All patients with out-of-hospital cardiac arrest were enrolled. The incidence of SCD was evaluated. Information about the patient's demographic data, the site of cardiac arrest, the mode of arrival, the duration of pre-arrest symptoms and if cardiopulmonary resuscitation was performed was gathered. Survival data at 3-year follow-up was obtained. Results: A total of 117 out of 769 (15%) patients met the criteria for SCD. Male gender was predominant, with a median age of 33 years. In about 79.5% of the patients, cardiac arrest was witnessed. Only 43 patients (36.8%) received cardiopulmonary resuscitation at the arrest site; 21 patients (17.9%) had a shockable rhythm and 96 patients (82.1%) had a non-shockable rhythm. Spontaneous circulation was returned in 15 patients (12.8%). Nine patients (7.7%) were discharged from the hospital and 8 (6.8%) survived at least 36 months. Conclusion: The study findings indicate the prevalence of SCD among patients who experienced a cardiac arrest outside the hospital. Unfortunately, only a small number of patients were able to survive in the long term. By implementing preemptive screening for individuals and their families, it may be possible to prevent SCD and improve outcomes for those affected. Keywords: Death, Sudden, Cardiac; Epidemiology; Etiology; Risk Factors; Incidence; Cardiopulmonary Resuscitation; Retrospective Studies; Oman

Loss of cerebrovascular Shaker-type K+ channels: a shared vasodilator defect of genetic and renal hypertensive rats

The cerebral arteries of hypertensive rats are depolarized and highly myogenic, suggesting a loss of K+ channels in the vascular smooth muscle cells (VSMCs). The present study evaluated whether the dilator function of the prominent Shaker-type voltage-gated K+ (KV1) channels is attenuated in middle cerebral arteries from two rat models of hypertension. Block of KV1 channels by correolide (1 μmol/l) or psora-4 (100 nmol/l) reduced the resting diameter of pressurized (80 mmHg) cerebral arteries from normotensive rats by an average of 28 ± 3% or 26 ± 3%, respectively. In contrast, arteries from spontaneously hypertensive rats (SHR) and aortic-banded (Ao-B) rats with chronic hypertension showed enhanced Ca2+-dependent tone and failed to significantly constrict to correolide or psora-4, implying a loss of KV1 channel-mediated vasodilation. Patch-clamp studies in the VSMCs of SHR confirmed that the peak K+ current density attributed to KV1 channels averaged only 5.47 ± 1.03 pA/pF, compared with 9.58 ± 0.82 pA/pF in VSMCs of control Wistar-Kyoto rats. Subsequently, Western blots revealed a 49 ± 7% to 66 ± 7% loss of the pore-forming α1.2- and α1.5-subunits that compose KV1 channels in cerebral arteries of SHR and Ao-B rats compared with control animals. In each case, the deficiency of KV1 channels was associated with reduced mRNA levels encoding either or both α-subunits. Collectively, these findings demonstrate that a deficit of α1.2- and α1.5-subunits results in a reduced contribution of KV1 channels to the resting diameters of cerebral arteries from two rat models of hypertension that originate from different etiologies