High systemic vascular resistance and sudden cardiovascular collapse in recovering Norwood patients

Sudden death, remote from surgery, in patients with hypoplastic left heart syndrome (HLHS) after Norwood palliation is an important problem. The episodic nature of this syndrome has made its cause(s) difficult to ascertain. Observations made in hospitalized Norwood patients may afford insight into the pathophysiology of sudden death among these patients.

We conducted a retrospective chart review.

Five patients with HLHS experiencing unremarkable recoveries from Norwood palliation, still hospitalized but extubated (only 1 in intensive care), had unexpected, acute decompensation 8 to 15 days postoperatively. All had acutely decreased peripheral perfusion; severe metabolic acidosis (mean HCO(3) = 9 mEq/L, range 6 to 11 mEq/L; mean arterial lactate = 16 mmol/L, range 10 to 20 mmol/L, normal less than 2 mmol/L); relatively high arterial pO(2), especially considering their low systemic perfusion (mean = 57 mm Hg, range 50 to 66 mm Hg on fraction of inspired oxygen (FiO(2)) less than 0.3 in 4 of 5 patients); and relatively high systolic blood pressure (mean systolic blood pressure = 91 mm Hg, range 78 to 116 mm Hg). During the preceding 24 hours, all had had systolic blood pressures of more than 85 mm Hg at multiple times. All were resuscitated with mechanical ventilation and administration of HCO(3) and intravenous inotropic agents or vasodilators (1 also required extracorporeal membrane oxygenation), with rapid resolution of their acidosis. After decompensating, all were treated with oral antihypertensive agents; 1 had an early hemi-Fontan. All survived to discharge.

Increased systemic vascular resistance may be especially pernicious in Norwood patients-even remote from operation-as the condition increases myocardial work and O(2) consumption while diminishing systemic perfusion. Chronic and acutely increased systemic vascular resistance may account for some cases of sudden unexpected death in Norwood patients.