Case scenarios Atrial switch Univentricular repair Dr.Yasser Salem

The case of Dr. Marwa Khyry

Atrial switch ??

Atrio-ventriculo-arterial sequence

Atrio-ventriculo-arterial sequence Concordance Normal sequence AV & VA Discordance Reversed sequence AV & VA Corrected TGA = AV discordance + VA discordance

Atrial switch Corrected TGA = AV discordance + VA discordance

Atrial switch Corrected TGA = AV discordance + VA discordance Anatomic consideration: Mustard operation Senning operation Corrected TGA = AV discordance + VA discordance

Atrial switch RV facing systemic pressure Functional consideration: RV facing systemic pressure Pulmonary hypertension may be present Baffle may leak or obstruct flow Suture line near the SA node

Mysterious RV

AFTERLOAD (MEAN PRESSURE) Mysterious RV Positive inotropes CO RV LV 45 mmHg 150 mmHg AFTERLOAD (MEAN PRESSURE)

Mysterious RV

Ventricular interdependence PVA SVA

Ventricular interdependence PVA SVA Atrial interdependence

Atrial switch RV facing systemic pressure Preoperative assesment: Functional consideration: RV facing systemic pressure Pulmonary hypertension may be present Baffle may leak or obstruct flow Suture line near the SA node Evaluation of RV function Evaluation of pulmonary pressure Evaluation of baffle status Evaluation of arrhythmias and pacemaker

Single ventricle physiology

Mixing lesions Defects with mixing of oxygenated and deoxygenated blood Partial desaturation lead to compensatory in red cell mass and increase 2,3 DPG with increase in blood viscosity.

Single ventricle physiology

Single ventricle physiology The driving force for Qp is SVC pressure Qp must pass through two separate and highly regulated vascular beds: cerebral and pulmonary vasculature Removes the left-to-right shunt and thus the volume load from the single ventricle

Single ventricle physiology

SVC Pressure Acute rise in SVC pressure Selection of patients with low PVR minimizes the risk from elevated SVC pressure Failure to maintain low SVC pressure lead to problems maintaining adequate SaO2 Small veno-venous collateral vessel contribute to arterial desaturation

Single ventricle physiology PSVC QPA : QSA = PPA – PPV x + PLA QPB : QSB

Single ventricle physiology PSVC - PLA QPA : QSA = PPA – PPV QPB : QSB PSVC - PLA = QPA : QSA PPA – PPV x QPB : QSB PSVC QPA : QSA = PPA – PPV x + PLA QPB : QSB

Minimize SVC Pressure Minimize use of positive pressure, including PEEP, following surgery Allow the end-expiratory lung volume to approximate FRC Minimal mean airway pressure and early extubation in patient with healthy lungs Negative-pressure ventilation associated with increased Qp Higher airway pressure to maintain FRC in pneumonia or ARDS Aprotinin and modified ultrafiltration:  transpulmonary pressure gradient, less pleural drainage, improved SaO2

Vascular Resistance Qp largely dependent on resistance of 2 highly but differentially regulated vascular beds Cerebral and pulmonary vasculatures Opposite responses to changes in CO2, acid-base status, and O2 Qp dependent on venous return through SVC (largely cerebral blood flow) Hyperventilation following bidirectional cavopulmonary anastomosis impair cerebral blood flow and decrease SaO2 Inhaled NO may be the best treatment for high PVR and low SaO2 after bidirectional cavopulmonary anastomosis

Volume Unloading The right-to-left shunt is eliminated and all Qp is effective pulmonary flow An acute increase in wall thickness and decrease in cavity dimension has been associated with improved tricuspid valve function Preload and afterload are both decreased Change in ventricular geometry may increase risk for systemic outflow obstruction in some

Single ventricle physiology Backward effect Systemic venous congestion Need for higher SVC pressure to drive flow in the shunt Forward effect Non pulsatile pulmonary flow Left atrial filling totally dependant on pulmonary flow Systemic hypotension

Single ventricle physiology Pitfalls Saturation is not sytemic pressure dependent Saturation is pulmonary pressure dependent All circulatory and ventilatory support should be directed to: Lower PVR Higher SVR Higher Rt filling pressure (within limits)

Single ventricle physiology Pitfalls (within limits) ↓PVR ↑SVR ↑CVP