Cardiology Flashcards
Causes of a long QT interval
Romano-Ward syndrome
Jervell-Lange-Nielsen syndrome
Cisapride
CNS/Head injury
Hypokalaemia
Erythromycin
Hypocalcaemia
Hypomagnesemia
Adrenal insufficiency
Hypothermia
Quinidine
Phaeochromocytoma
Aneurysms of the vein of Galen
Presentation
Ix
Mx
Prognosis
The vein of Galen is located under the cerebral hemispheres and drains the anterior and central regions of the brain into the sinuses of the posterior cerebral fossa.
Aneurysmal malformations of the vein of Galen (VGAM) typically result in high-output congestive heart failure or may present with developmental delay, hydrocephalus, and seizures
Cranial USS will help to localize or identify the lesion. Doppler studies can help further to understand the hemodynamics of the lesion.
MRA can help to delineate the vascular supply
Mx
Endovascular embolization is the first option for treatment.
Cardiology consult for high output cardiac failure
More thanhalf of patients with VGAM have a malformation that cannot be corrected. Patients frequently die in the neonatal period or in early infancy.
How does Prostacyclin work
Prostacyclin is a vasodilator derived from arachidonic acid via the cycloocygenase pathway. It also acts toinhibit platelet aggregation and hence clot formation. It antagonises the effects of thromboxane A2.
It is an endothelium derived vasodilator
What does Endothelin 1 do
Endothelin 1 is a potent vasoconstrictor polypeptide
How does Nitric oxide work
Nitric oxide, also known as endothelium-derived relaxing factor, is a substance formed from arginine in endothelim cells that acts on vascular smooth muscle cells to cause vasodilation. It is inactivated by haemoglobin.
Endothelial cells secrete which three major substances.
Nitric oxide
Prostacyclin
Endothelin 1
Thromboxane A2
Thromboxane A2, another product of the cyclooxygenase pathway, is produced by activated platelets and has prothrombotic properties.
Angiotensin II formation
Angiotensin II is formed from angiotensin I in the plasma by angiotensin-converting enzyme (ACE). The majority of ACE is located in the endothelial cells, with most of the conversion of angiotensin I to II occurring as the blood passes through the lungs. Angiotensin I is derived from angiotensinogen, which is produced by the liver.
Prostaglandin H2
Prostaglandin H2 is an arachidonic acid derivedprecusor for various other prostaglandins, prostacyclin and thromboxane A2. It is produced by many bodily tissues.Cell membrane phospholipids are converted to arachidonic acid by the action of phospholipase A2. In turn, prostaglandin H2 is formed via the action of COX1 and COX2. Prostaglandin H2 has no vasoactive function.
Angiotensin-converting enzyme inhibitors
Examples
Use in cardiac failure
Angiotensin-converting enzyme inhibitors (captopril, enalapril, and lisinopril) are first-line therapy in patients with heart failurerequiring long-term treatment. These agents, which block angiotensin II-mediated systemic vasoconstriction, are particularly useful in children with structurally normal hearts but reduced LV myocardial function (i.e. myocarditis or dilated cardiomyopathies).
Oral afterload-reducing agents improve cardiac output by decreasing systemic vascular resistance. These agents are also useful in ameliorating mitral and aortic insufficiency and have a role in controlling refractory heart failurein patients with large left-to-right shunts in whom systemic vascular resistance is elevated.
Which drugs most commonly cause prolonged QTc
A long QT interval is most frequently seen with class I (flecanide, lidocaine) and class III (sotalol, amiodarone) antiarrhythmic drugs.
Other classes of drugs that cause QTc prolongation include antihistamines, antidepressants (e.g. imipramine), antibiotics (e.g. erythromycin), antifungal drugs (e.g. ketoconazole)and antipsychotics. Cisapride is also known to cause long QT.
Stages are repair of HLHS
Norwood procedure at around one week of life where the aortic arch is reconstructed using the PA and connected to the RV which can then supply systemic circulation. Pulmonary blood flow classically is established via a BT shunt between the innominate artery and PA however variations of this can occur.
Glenn procedure at three-six months occurs when the patient outgrows the BT shunt becoming progressively more cyanotic. The BT shunt is removed and the SVC is connected to the PA providing systemic venous return directly to the pulmonary artery.
Fontan procedure at two-five-year-old involves connecting the IVC to the PA so the entire systemic venous return flows to the pulmonary artery, thereby relieving cyanosis.
LQT1 and LQT2 electrolyte abnormality
Prolonged potassium efflux is seen in LQT1 and LQT2 resulting in prolonged QT interval
The differential diagnosis for widely fixed S2 includes:
Volume overload e.g. ASD, PAPVR
Pressure overload e.g. PS
Electrical delay e.g. RBBB
Early aortic closure e.g. MR
Occasional normal child
The second heart sound has two components. The first is A2, followed by P2, corresponding to the closure of the aortic and pulmonary valves respectively. Normal slitting of S2 is characterised by an increase with inspiration as blood flows into the right heart, prolonging RV emptying, followed by decreased splitting or single S2 with expiration. The absence of splitting, or wide, fixed, narrow or reverse splitting indicates abnormality.
The incidence of RBBB approaches 80% post Fontan procedure, secondary to incision into the right ventricular wall during reconstruction of the right ventricular outflow tract. RBBB results in delayed electrical activation of the right ventricle with a subsequent delay in closure of the pulmonary valve. The end result is a widely split second heart sound.
