Keywords

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Damus–Kaye–Stansel Operation

  • Surgical operation performed in TGA, single ventricle, and restrictive VSD causing subaortic stenosis.

  • Side-to-side aorta and pulmonary artery connection to provide unrestricted blood flow from the systemic ventricle to the aorta.

D-Dimers

  • High negative predictive value for PE and DVT.

  • Positive D-dimer results with medium–high clinical probability of PE should be followed by CTA.

Dextrocardia

  • Anomalous cardiac position with the apex pointing the right chest wall.

  • Cardiac anatomy may be normal.

  • Check for other congenital cardiac lesions.

  • Differential diagnosis: in case of abnormal heart position, look for congenital absence of pericardium.

Diastolic Dysfunction

Diastolic Tail

DiGeorge Syndrome

  • Genetic disease on chromosome 22 leading to thymic hypoplasia with low T cell count, hypoparathyroidism with hypocalcemia, and outflow tract defects of the heart (ToF, truncus arteriosus, interrupted aortic arch, right-sided aortic arch, aberrant right subclavian artery).

Dilated Cardiomyopathy

  • Impaired systolic function with dilatation of cardiac chambers.

  • Diastolic function can be normal or impaired.

  • Causes: inherited (25 %), myocarditis, metabolic, nutritional, and persistent tachycardia. Usually diagnosis of exclusion.

  • Differential diagnosis: ischemic heart disease, valvular disease, adult congenital heart disease, left ventricular noncompaction, iron-overloaded cardiomyopathy, alcoholic cardiomyopathy, hypertensive heart disease.

  • See also section Cardiomyopathies.

Dipyridamole

  • Indirect vasodilator agent used in stress MR.

  • Increase endogenous levels of adenosine blocking cellular uptake.

  • Dipyridamole dose: 0.56 mg/kg IV over 4 min.

  • Prolonged action (~30 min).

  • Low-dose protocol: infusion of a total dose of 0.56 mg/kg dipyridamole in 4 min, with imaging started immediately after completion of the 4 min infusion.

  • High-dose protocol: adds a second injection of 0.28 mg/kg dipyridamole for 2-min duration, with imaging initiated at 8 min after the beginning of the first injection (a total dose of 0.84 mg/kg dipyridamole is injected in the high-dose dipyridamole infusion protocol).

  • Patients should avoid methylxanthine-containing products for 24 h prior the scan.

  • Contraindications: (1) high-grade AV block; (2) asthma or COPD; (3) sinus bradycardia; (4) systemic hypotension (BP <90 mmHg); (5) severe carotid stenosis.

  • Side effects: transient heart block, transient hypotension, transient tachycardia, bronchospasm.

  • Antagonist: aminophylline, 50–100 mg over 1 min, injection can be repeated up to 250 mg total dose.

  • See also section “Perfusion imaging, myocardial”.

Dobutamine

  • Positive inotropic agent used in stress MR.

  • Increases heart rate and myocardial contractility.

  • High-dose protocol: IV dobutamine infusion at 3 min stages (10, 20, 30, 40 μg/kg/min).

  • Target heart rate: (220 age) × 0.85. If not reached at 40 μg/kg/min, atropine in 0.25 mg fraction (2 mg max.) if heart rate response is poor.

  • Low-dose protocol: 5–10 μg/kg/min.

  • Contraindications: (1) severe hypertension (>220/120 mmHg); (2) congestive heart failure; (3) unstable angina (4) aortic valve stenosis (peak gradient >50 mmHg); (5) HCM; (6) complex arrhythmias; (7) myocarditis; (8) pericarditis.

  • See also section “Perfusion imaging, myocardial”.

Dominance, Coronary

  • Coronary artery dominance refers to which artery supplies the posterior part of the heart.

  • In 85–90 % is the right coronary artery (right dominance).

  • In 8–10 % is the circumflex artery (left dominance).

  • In 5 % the inferior wall is vascularized both from RCA and Cx (codominant or balanced circulation).

Dose Length Product

  • DLP: CTDI vol × scan length.

  • It is an indicator of total exposure for a complete CT scan, which allows us to compare the dose with several adjustments of technical parameters in order to optimize patient protection.

Double Outlet Right Ventricle

  • >50 % of great vessels arise from the right ventricle.

  • Large subaortic VSD.

  • Wide abnormalities spectrum: from Fallot type to transposition of the great arteries.

  • Can be associated with RVTO stenosis.

  • MR: (1) vascular connection, (2) ventricular volumes and function, (3) RVTO stenosis, (4) shunts.

Dressler Syndrome

  • A myocardial infarction-associated pericarditis with delayed onset typically 1 week after infarction to several months.

  • Suspected autoimmune etiology.

Ductus Arteriosus or Ductus Botalli

  • A fetal blood vessel connecting the pulmonary artery to the aortic arch.

  • Fibrosis and closure at birth (ligamentum arteriosum).

Ductus Arteriosus, Persistent

  • Left-to-right extracardiac shunt caused by patent ductus arteriosus.

  • MR: (1) shunt detection; (2) quantification of shunt degree.

Dyslipidemia

  • Primary hyperlipidemias: (1) familial hyperchylomicronemia; (2) familial hypercholesterolemia; (3) familial defective apoprotein B-100; (4) polygenic hypercholesterolemia; (5) familial combined hyperlipidemia; (6) dysbetalipoproteinemia; (7) familial hypertriglyceridemia; (8) type V hyperlipoproteinemia.

  • Secondary hyperlipidemias: (1) renal failure; (2) nephrotic syndrome; (3) hypothyroidism; (4) type II diabetes and obesity; (5) alcohol abuse; (6) cholestasis; (7) drugs.

  • Normal range for plasma lipid levels: (1) total cholesterol, 150–250 mg/dL; (2) LDL cholesterol, <160 mg/dL; (3) HDL cholesterol, 30–75 mg/dL; (4) triglycerides, 70–175 mg/dL.

Dyssynchrony, Cardiac

  • Three types: (1) atrioventricular (PR > 120 ms); (2) interventricular (delay between RV and LV contraction); (3) intraventricular (differences in regional wall motion).

Dystrophies, Muscular

  • Hereditary muscle disease causing progressive severe skeletal muscle weakness, which can lead to dilated cardiomyopathy.

  • Most common: Duchenne, Becker, limb girdle muscular dystrophies.

  • MR: (1) left ventricle dysfunction; (2) myocardial edema and inflammation; (3) late enhancement similar to myocarditis.