Which of the following is most common type of atrial septum defect (ASD)?

Appeared in: NORCET-7 Mains-2024

Explanation

Ostium secundum is the most prevalent type of atrial septal defect, accounting for approximately 90% of all cases.
This defect is located in the central part of the atrial septum, specifically in the region of the fossa ovalis.
It results from either inadequate growth of the septum secundum or excessive resorption of the septum primum during fetal development.
Due to its high prevalence, it is the type of ASD most commonly encountered in clinical practice.

Option A: Ostium primum defects are significantly less common than ostium secundum defects, comprising only about 5% of all ASDs.
Option C: Sinus venosus defects are also uncommon, accounting for about 5% of ASDs.
Option D: This option is incorrect because a correct answer, Ostium secundum, is listed among the choices as the most common type of ASD.

Visual 1: Diagram - An illustration of the heart's atrial septum, clearly marking the locations of the three main types of ASDs: Ostium Secundum (central), Ostium Primum (low), and Sinus Venosus (high). This visual helps in understanding the anatomical basis of the classification.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Types and prevalence of Atrial Septal Defects (ASD) as background academic context rather than a clinical decision trigger.
Nurses caring for patients with ASD must monitor for signs of right-sided heart failure (e.g., peripheral edema, jugular venous distension, hepatomegaly) which can result from chronic volume overload on the right ventricle due to the left-to-right shunt.
A key patient safety concern is the risk of paradoxical embolism. An ASD allows venous clots to bypass the pulmonary circulation and enter the systemic arterial system, potentially causing a stroke or other systemic emboli.
Atrial arrhythmias, particularly atrial fibrillation or flutter, are common long-term complications due to right atrial enlargement and stretching from chronic volume overload.

How to Approach the Question

First, identify the key phrase in the question: "most common type". This indicates the question is asking for the most prevalent form of a condition.
The question is about Atrial Septal Defect (ASD). This is a factual recall question requiring knowledge of congenital heart diseases.
Recall the main classifications of ASD: ostium secundum, ostium primum, and sinus venosus.
Compare the known prevalence of each type. Ostium secundum is by far the most frequent.
Select the option that matches this fact.
Eliminate the other options as they represent less common forms of ASD, and rule out "None of the above" since a correct option is present.

Concept Tested & Keywords

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Practise the full NORCET-7 Mains-2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.