Lecture 11: Congenital Cardiac Disease

What is a patent ductus arteriosus?

connection between aorta and pulmonary artery (persistent patency of feta vessel connecting the two) resulting in  left atrial & ventricular enlargement, Left heart volume overload, Pulmonary overcirculation

How is PDA diagnosed?

Physical exam

• Most asymptomatic and cardiac murmur leads to workup

• stunted size compared to littermates

• Continuous murmur left heart base (washing machine)

• Bounding arterial pulses

• If CHF has developed, usually left heart failure with dyspnea, crackles

ECG: variable

Thoracic rads:

• Cardiomegaly: can see generalized or mostly left heart enlargement

• Pulmonary overcirculation

• 3 bumps: aorta at 1:00, pulmonary artery at 2:00, left auricular appendage at 2:00-3:00

Echo:

• Left heart volume overload

• Continuous flow main pulmonary artery

• PDA visualized

What congenital defect is seen on this rad?

PDA

What is the treatment for PDA?

interventional closure:

• minimally invasive coil or amplatz (ACDO) occlusion

• thoracotomy

You are presented with a puppy who is the runt of the litter. Upon physical exam, you find left basilar continuous murmur and bounding femoral pulses. What congenital defect are you worried about? What potential complications of this defect?

PDA

Complications:

• Left-sided congestive heart failure

• Can cause secondary pulmonary hypertension → shunt reversal → differential cyanosis, erythrocytosis (can’t be repaired if reverses)

What is a ventricular septal defect?

communication between L & R ventricle due to a defect in the interventricular septum → results in left atrial and ventricular enlargement, left heart volume overload (L to R shunting), and pulmonary overcirculation

most common defects in horses, ruminants, cats (english bulldog, keeshond, maltese predisposed)

How are VSDs diagnosed?

What defect is most likely affecting this cat? note the pulmonary overcirculation and cardiac enlargement.

VSD in a cat with CHF

What is the treatment for VSDs?

• Medical therapy for CHF

• Pulmonary Artery Banding

• If muscular VSD then Amplatz occlusion possible (very uncommon)

• Surgical Repair

  • Requires Cardiopulmonary Bypass

  • Patch applied over the VSD

  • Uncertain operative mortality

True or false: louder murmurs are usually associated with smaller VSDs?

true

What is an atrial septal defect?

communication between L & R atrium due to a defect in the intra atria septum → results in right atrial and ventricular enlargement, right heart volume overload, and pulmonary overcirculation → may progress to pulmonary hypertension and right sided heart failure

True or false: ASDs are usually seen on their own.

false: they are most frequently seen with other defects

Who is predisposed to ASDs?

• Samoyed, Doberman, Standard poodle, Old English Sheepdog

• Cats, ruminants rarely

How are ASDs diagnosed?

What is the treatment for ASDs?

• Medical therapy for CHF

• Occluder devices

• Surgical Repair

  • Requires Cardiopulmonary Bypass

  • Patch applied over the ASD

  • Uncertain operative mortality

  • Rare

What is pulmonic stenosis?

narrowing of the pulmonary outflow tract due to valvular stenosis, subvalvular stenosis, supravalvular stenosis → RV creates increased pressure to maintain normal PA pressure → RV concentric hypertrophy, post-stenotic dilation of pulmonary a., secondary tricuspid regurgitation can develop

Who is predisposed to pulmonic stenosis?

• English Bulldog, Schnauzer, Beagle, Chihuahua, Terrier breeds, Cocker Spaniels, Samoyed, Bassett hound

• English Bulldog & Boxer can have anomalous coronary vessel which encircles PA

• Cat: Isolated pulmonic stenosis rare

How is pulmonic stenosis diagnosed?

What defect has most likely caused these cardiac changes?

pulmonic stenosis

How is pulmonic stenosis treated?

• Beta Blocker – reduce RV workload & risk for sudden death

  • Decr. HR = more RV filling time

  • Decr. Contractility = reduced pressure buildup near PS

  • Decreases risk for arrhythmias

• Medical therapy for CHF

• Balloon Valvuloplasty

What is the prognosis of pulmonic stenosis?

• Mild – excellent, monitoring only

• Moderate – good with monitoring or intervention

• Severe – guarded without intervention

What is subaortic stenosis

Narrowing of the aortic outflow tract: fibromuscular ridge below the aortic valve → high left ventricular pressures → left ventricular concentric hypertrophy

common in large breed dogs (Newfoundland, Goldens, Rottweilers)

How is subaortic stenosis diagnosed?

What is the treatment for subaortic stenosis?

• Beta Blocker – reduce LV workload & risk for sudden death

  • Decr. HR = more LV filling time

  • Decr. Contractility = reduced pressure buildup near SAS

  • Decreases risk for arrhythmias

• Medical therapy for CHF

• Balloon valvuloplasty - high pressure balloon

• Surgical removal of subvalvular fibrous ring - No clear-cut improved outcome

What is AV valve dysplasia?

• Congenital malformation of the mitral or tricuspid valve

• Results in regurgitation (+/- stenosis)

• Volume (or pressure) overload of the affected atrium & ventricle

• Valve leaflets thickened or fused

• Abnormal chordae tendinae (short or long)

• Abnormal papillary muscles: Malpositioned, Incomplete or absent, Abnormal attachment to ventricular wall

• Common defect in the cat

• Lab, Great Dane, GSD, Weimaraner

What are the physical exam findings of AV valve dysplasia?

How is AV valve dysplasia diagnosed?

Thoracic rads:

• cardiomegaly (LA or RA enlargement)

• pulmonary venous congestion/edema (MVD)

• pleural effusion, hepatomegaly, ascites (TVD)

ECG:

• atrial enlargement (tall or wide P waves)

• ± ventricular enlargement and arrhythmias

Echo:

• abnormal valve morphology (thickened, shortened, displaced leaflets)

• color doppler: regurgitant jet or stenosis

How is AV valve dysplasia treated and what is the prognosis?

What are the 4 key abnormalities that together cause the right to left shunting and systemic hypoxemia of tetralogy of fallot?

• VSD

• Pulmonic stenosis

• RV hypertrophy

• Overriding aorta over VSD)

What are the forms of tetralogy of fallot?

Classic/Typical/Pulmonic stenosis dominant*

• Cyanosis, exercise intolerance, polycythemia

VSD Dominant

• Pulmonary overcirculation, no cyanosis

Balanced Tet

• Moderate PS and VSD

• Mild or intermittent cyanosis, subtle signs

How is tetralogy of fallot diagnosed?

How is tetralogy of fallot treated?

• Beta Blocker – reduce dynamic RVOT obstruction and improve exercise tolerance

• Medical therapy for CHF

• Repeated phlebotomy or hydroxyurea for polycythemia

• Palliative surgery: Modified Blalock-Taussig shunt to increase pulmonary blood flow (uncommon)

What are the causes of right to left shunting?

Tetralogy of Fallot

Eisenmenger’s physiology (pulmonary hypertension)

• VSD with pulmonary hypertension (Eisenmenger’s syndrome)

• ASD with pulmonary hypertension

• PDA with pulmonary hypertension (differential cyanosis)

What are the clinical signs of right to left shunting?

• Cyanosis

• Reduced exercise tolerance (syncope)

• Polycythemia

• Neurologic signs, seizures

  • Capillary sludging due to polycythemia

  • Paradoxical embolism

  • Thrombus - infarct

  • Bacteria – CNS abscess