Atrial septal defect pathophysiology

Jump to navigation Jump to search
https://https://www.youtube.com/watch?v=ed6__8FaSOU%7C350}}

Atrial Septal Defect Microchapters

Home

Patient Information

Overview

Anatomy

Classification

Ostium Secundum Atrial Septal Defect
Ostium Primum Atrial Septal Defect
Sinus Venosus Atrial Septal Defect
Coronary Sinus
Patent Foramen Ovale
Common or Single Atrium

Pathophysiology

Epidemiology and Demographics

Risk Factors

Natural History and Prognosis

Complications

Diagnosis

History and Symptoms

Physical Examination

Electrocardiogram

Chest X Ray

CT

MRI

Echocardiography

Transesophageal Echocardiography
Transthoracic Echocardiography
Contrast Echocardiography
M-Mode
Doppler

Transcranial Doppler Ultrasound

Cardiac Catheterization

Exercise Testing

ACC/AHA Guidelines for Evaluation of Unoperated Patients

Treatment

Medical Therapy

Surgery

Indications for Surgical Repair
Surgical Closure
Minimally Invasive Repair


Robotic ASD Repair
Percutaneous Closure
Post-Surgical Follow Up

Special Scenarios

Pregnancy
Diving and Decompression Sickness
Paradoxical Emboli
Pulmonary Hypertension
Eisenmenger's Syndrome
Atmospheric Pressure

Case Studies

Case #1

Atrial septal defect pathophysiology On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Atrial septal defect pathophysiology

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Atrial septal defect pathophysiology

CDC on Atrial septal defect pathophysiology

Atrial septal defect pathophysiology in the news

Blogs on Atrial septal defect pathophysiology

Directions to Hospitals Treating Type page name here

Risk calculators and risk factors for Atrial septal defect pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [3]

Overview

In a normal heart, the typical path of blood flow is to flow from right-to-left allowing for blood to leave the deoxygenated right system and become oxygenated in the left system. In patients with an atrial septal defect, the typical path of blood flow is disrupted by the septal opening. This results in blood shunting from left-to-right. The severity of circulatory complications depends largely on the size of the defect. The larger the defect between the septal walls, the greater the amount of mixing between deoxygenated and oxygenated blood. Flow from the left atrium into the right atrium increases flow through the pulmonary circuit increasing the load on the right ventricle and slowly injuring the pulmonary vasculature over time.

Pathophysiology

Left-Sided Versus Right-Sided Pressures

In unaffected individuals, the chambers of the left side of the heart make up a higher pressure system than the chambers of the right side of the heart. This is because the left ventricle has to produce enough pressure to pump blood throughout the entire body, while the right ventricle only has to produce enough pressure to pump blood to the lungs.

Calculation of the Pulmonary to Systemic Flow Ratios

In the case of a large ASD (>9 mm), which may result in a clinically significant left-to-right shunt, blood will shunt from the left atrium to the right atrium causing excessive mixing of the blood between the two atria. In a hemodynamically significant ASD, Qp is the pulmonary flow and Qs is the systemic flow and the Qp:Qs > 1.5:1). If the Qp:Qs is > 1.5:1, then the patient is often symptomatic, and a repair of the ASD may be indicated. This extra blood from the left atrium may cause a volume overload of both the right atrium and the right ventricle, which if left untreated, can result in enlargement of the right side of the heart and ultimately right-sided heart failure.

Impact of Changes in Left Ventricular Loading Conditions

Any process that increases the pressure in the left ventricle can cause worsening of the left-to-right shunt. This includes hypertension, which increases the pressure that the left ventricle has to generate in order to open the aortic valve during ventricular systole, and coronary artery disease which increases the stiffness of the left ventricle, thereby increasing the filling pressure of the left ventricle during ventricular diastole.

Right Heart Failure as a Consequence of Left Right Shunting

The right ventricle will have to push out more blood than the left ventricle due to the left-to-right shunt. This constant overload of the right side of the heart will cause an overload of the entire pulmonary vasculature. Eventually the pulmonary vasculature will develop pulmonary hypertension as a result of the extra blood flow through the lungs.

The resulting pulmonary hypertension will cause the right ventricle to face increased pressure or increased afterload in addition to the increased preload (higher volume coming into the right side of the heart) as a result of the shunted blood flowing from the left atrium into the right atrium. The right ventricle will be forced to generate higher pressures to try to overcome the pulmonary hypertension. This may lead to right ventricular failure (dilatation and decreased systolic function of the right ventricle). Eventually the right-sided pressures may exceed left-sided pressures.

Equalization of Left and Right Atrial Pressures

When the pressure in the right atrium rises to the level in the left atrium, there will no longer be a pressure gradient between these heart chambers, and the left-to-right shunt will diminish or cease.

Development of Right-to-Left Shunting or Eisenmenger's Syndrome

If left uncorrected, the pressure in the right side of the heart will be greater than the left side of the heart. This will cause the pressure in the right atrium to be higher than the pressure in the left atrium. This will reverse the pressure gradient across the ASD, and the shunt will reverse; a right-to-left shunt will exist. This phenomenon is known as Eisenmenger's syndrome. Once right-to-left shunting occurs, a portion of the oxygen-poor blood will get shunted to the left side of the heart and ejected to the peripheral vascular system. This will cause signs of cyanosis. once Eisenmenger's syndrome develops, the patient can no longer benefit from surgery to correct the defect.

Gross Pathology

Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

Associated Conditions

Secundum ASD is seen in Holt-Oram Syndrome with obvious limb malformations.

References


Template:WikiDoc Sources CME Category::Cardiology