A 28-year-old man was admitted after CPR due to ventricular fibrillation and in incipient cardiogenic shock based on newly diagnosed dilated cardiomyopathy. Past medical history was insignificant.
Physical examination and laboratory findings on admission:
ECG (on admission): sinus rhythm, heart rate 93 bpm, PQ 200ms, QRS 128ms, QTc 497ms, right axis deviation, flattened T in I, aVL, negative T in V6, rS V1-V5
Chest radiograph (on admission): enlargement of cardiac silhouette with markedly prominent left cardiac contour, enlarged hilar vessels without increased peripheral pulmonary vascular markings
Transthoracic and transoesophageal echocardiography showed the following findings:
Video 1 TTE examination on admission
Video 2 TEE examination showing ASD
Video 3 TEE confirming ASD
Image 1 Size of ASD
Cardiac MR finding corresponded to dilated cardiomyopathy, late gadolinium enhancement was present in the septal area.
Coronary angiography showed no significant coronary artery stenosis.
Right heart catheterization was performed with following findings.
CT angiography was subsequently performed and ruled out anomalous pulmonary venous return.
During hospitalization, the patient had a good response to milrinone. Initially, small doses of inotropes were needed. In the further course of hospitalization, the patient was hemodynamically stable without inotropic and vasopressor support. The pharmacological treatment of congestive cardiac failure was prescribed (ACE inhibitor, beta-blocker, aldosterone antagonist, diuretics, ivabradine). ICD implantation was indicated and performed for secondary prevention of sudden cardiac death.
Closure of the atrial septal defect was not indicated because of the severe LV dysfunction. The patient was placed on the waiting list for orthotopic heart transplantation.
Due to early need for re-hospitalization for signs of low cardiac output he was put on an urgent waiting list of HTx and successfully underwent transplantation 4 months after initial episode of heart failure.
CLINICAL CONTEXT AND LEARNING POINTS
Dilated cardiomyopathy (DCM) is characterized by dilation of one or both ventricles with impaired systolic function and may or may not develop overt heart failure. DCM is caused by a variety of disorders, although frequently no etiology can be found and the cardiomyopathy is deemed idiopathic. Causes of DCM include stress-induced, infectious, toxic, genetic, peripartum, tachycardia-mediated cardiomyopathy, sarcoidosis, end-stage kidney disease, autoimmune disease, endocrine dysfunction, and nutritional deficiencies. Current major society classification systems for cardiomyopathy exclude heart disease secondary to coronary artery disease, valvular or congenital heart disease.
Atrial septal defect (ASD) is the most common congenital heart lesion in adults and is often asymptomatic until adulthood. ASDs in adults are associated with left-to-right shunt causing volume overload of the right heart chambers and pulmonary arteries with possible late development of progressive pulmonary vascular obstructive disease and pulmonary hypertension. The severity of the shunt is determined by the size of the defect and atrial and ventricular compliance and pressure.
There are four major types of atrial septal defects (Image 2):
METHODS OF CARDIAC SHUNT QUANTIFICATION
Qp:Qs RATIO USING INVASIVE OXIMETRY
Invasive oximetry using Fick’s principle for the quantification of left-to-right shunting is based on measurements of blood oxygenation. Interventional closure or corrective surgery is usually indicated in patients with a Qp:Qs ratio >1.5.
Percentage oxygen saturation is required from the following: SVC, IVC, RA, RV, PA, PCW, aorta x2
* An increase in O2 blood saturation can be detected, typically an increase of more than 7% suspect a shunt
Mixed venous (MV) blood = (3xSVC + 1xIVC) / 4
* Blood saturation in IVC is affected by low blood desaturation in the kidneys
Since pulmonary veins are rarely entered during a cardiac cath, a pulmonary catheter wedge sample or LA sample (if the LA is entered through the ASD) can be used in its place !!! Alternatively, arterial saturation can be substituted !!!
Image 3. 'Oximetry run' in a patient with atrial septal defect. The 'step-up' detected in the right atrium (RA) identifies a left-to-right shunt at this location.
Qp:Qs RATIO USING DOPPLER ECHOCARDIOGRAPHY
The volume of fluid moving via a tube may be calculated by multiplying the cross-sectional area (CSA) by the velocity at which the fluid is moving. Thus, one may use CSA of the left and right ventricular outflow tracts (RVOT and LVOT) and respective summated average velocities during systole to determine the flow through the right and left circulations. Outflow tract diameters are obtained in the parasternal short and long axis, respectively. Pulsed wave Pulse doppler through the outflow tracts yields a spectral envelope which one may trace and yield a velocity time integral (VTI).
Formula: Qp:Qs= CSA RVOT x RVOT VTI(CSA LVOT) x (LVOT VTI)
Where to measure (Image 4)?
Suspicion on cardiac shunt already from right heart cath
Signs of recirculation should be investigated on transpulmonary thermodilution measurements of cardiac output (Image 5).
ASD closure in patients with severe dysfunction of LV
Concomitant LV dysfunction causes an increase in LV end-diastolic and left atrial (LA) pressure. In the setting of an ASD, this results in increased left to right shunting and provides a means of “offloading” the less compliant left ventricle. Abrupt closure of this interatrial communication in the setting of transcatheter closure results in an acute increase in left ventricular and left atrial filling pressures as well as myocardial oxygen consumption and may lead to acute decompensation of the left ventricle and pulmonary oedema.
Due to aforementioned reasons, our patient was not indicated for ASD closure due to expected deterioration after the procedure. Patient was indicated for heart transplant.
Authors: Michal Pazderník, Erik Schmotzer