General Principles

Patients are generally classified as having simple, moderately complex and complex congenital heart disease according to the Canadian Consensus definitions, with increasing complexity of disease associated with higher ICU interventions, morbidity and mortality. Approaching such patients when critically ill demands application of a number of basic principles. The first principle of GUCH ICU management is to understand the cardiopulmonary anatomy of the individual patient. This involves knowledge of the primary lesion, the type of any corrective/palliative surgery or intervention performed, and the presence of any residual haemodynamic lesions – either dynamic or fixed. Second, an understanding of the normal physiology of the patient is essential. This includes the normal haemoglobin, oxygen saturations, systemic and pulmonary blood pressure and surface electrocardiogram. Third, the ICU clinician must consider how the effects of any supportive and therapeutic interventions might affect the circulation. This is of particular importance in the univentricular heart, in the presence of systemic-pulmonary shunts and in the Fontan circulation. In GUCH patients (particularly where complex) performance of relatively simple investigations and interventions may differ from those in the non-GUCH population. In addition to the basic anatomy and physiology, there are further aspects relevant to ICU care that must be considered in this patient population (Table 51.1).

In all patients, close liaison between specialists in GUCH, heart failure, congenital cardiac surgery and echocardiography is crucial as the management of such patients demands a multidisciplinary approach^.

The Cyanotic Patient

Cyanotic congenital heart disease is not a contraindication to ICU admission as such patients may have a relatively good prognosis, with mortality generally related to the admission diagnosis. The cyanotic patient has adaptive mechanisms to increase oxygen delivery, including a rightward shift in the oxyhaemoglobin dissociation curve, an increase in cardiac output, and an increased haematocrit. The resultant erythrocytosis may result in the hyperviscosity syndrome; however routine venesection is not recommended, and iron deficiency in these patients is common. Haemostatic changes including abnormalities of prothrombin time, partial thromboplastin time, factors V, VII, VIIII, IX and thrombocytopenia have been documented, but will not usually require treatment. When assessing the cyanotic patient, citrate bottles adjusted for the haematocrit must be used.

Renal dysfunction is common and occurs due to the combination of hyperviscosity with arteriolar vasoconstriction, resulting in renal hypoperfusion and progressive glomerulosclerosis, manifesting as proteinuria, hyperuricaemia or varying degrees of renal failure. Where a cyanotic patient is admitted with abnormal neurology, headache or is postictal, a high index of suspicion should exist for intracerebral thrombosis, haemorrhage or abscess. Where intravenous contrast is used, the patient must be well hydrated, and the minimal amount of contrast used as possible, as there is the potential to develop marked hyperkalaemia following administration.

The Failing Morphological Right Ventricle

The morphological right ventricle (RV) may be subpulmonary, subaortic or be the only effective ventricle in the univentricular heart. Causes of right ventricular dysfunction include previous cardiac surgery, pulmonary hypertension, Ebstein’s anomaly, a significant shunt, systemic RV and volume overload. The subpulmonary failing RV may be supported using standard inotropic agents whilst avoiding pulmonary vasoconstrictors. Cardiac output may be maintained or improved by minimising RV afterload: minimising ventilator pressures, drainage of pleural collections, bronchodilation, the use of pulmonary vasodilators and early extubation.

Where the morphological RV is systemic (congenitally corrected transposition of the great arteries (ccTGA) and transposition of the great arteries (TGA) with Mustard/Senning) and failing, treatment is challenging. Reversible causes (including arrhythmia and volume overload) should be aggressively sought and treated. Although systemic RV fibrosis is common, the coronary arteries are usually angiographically unobstructed. Standard management of the failing systemic ventricle should be used, including pharmacological and mechanical support, but these may not be effective. In some centres the use of multisite RV pacing has been used with good effect.

The Univentricular Heart

This presents many challenges, from prevention of air embolism, to the unpredictability of the effects of vasoactive agents and the adverse effects of positive pressure ventilation. It is important to know the current and most previously documented function of the single ventricle (morphologically right or left), as recent rapid deterioration is often due to development of an arrhythmia. Expert echocardiography is indicated. When considering the use of inotropic and vasoactive agents, the nature of the pulmonary connections must be considered. Where the pulmonary vasculature is protected by PA banding, the relative effects of pulmonary versus systemic constriction or dilatation may be different when compared with where there is an absent pulmonary connection with systemic-pulmonary collaterals/shunts. In the patient with absent pulmonary connection and systemic-pulmonary collaterals/shunts a small increase in PVR may result in a significant reduction in pulmonary blood flow and desaturation. In contrast, an increase in SVR and/or a fall in PVR may result in an increase in systemic-pulmonary shunting with fall in cardiac output. Attention should also be paid to oxygen administration, as this may also alter the balance between pulmonary and systemic circulation.

Arrhythmia

The commonest indication for hospital admission in the GUCH population is arrhythmia, and on occasion this will require ICU admission, or input from the critical care team. The management of arrhythmia in the ACHD ICU population is complex; however some general principles should be considered. First, the diagnosis of an arrhythmia may be challenging; atrial tachycardia may mimic sinus tachycardia to the non-expert. Here, comparison with previous 12-lead ECGs is useful, and where a pacemaker is implanted, interrogation may be critical in making the diagnosis. Second, as there is a high incidence of thyroid dysfunction and amiodarone prescription in the GUCH population, thyroid function tests should be performed upon diagnosis of a tachycardia or bradycardia. Third, although patients with a univentricular circulation in atrial tachycardia may tolerate a tachyarrhythmia well initially, decompensation may be rapid, and cardioversion should be considered at the earliest opportunity. Such patients should be managed by the most senior clinician, as cardioversion to a malignant arrhythmia is not uncommon, and as there may be no venous access to the heart. Transcutaneous pacing must always be available.

Heart Failure

The causes of heart failure in the GUCH population include one or more of: impaired ventricular function (left or right), volume overload, arrhythmia, valve lesions or an excessive shunt. Once an arrhythmia has been excluded, echocardiography is required to make or confirm the diagnosis. Where indicated, urgent surgical or catheter intervention may be required. Pre-optimisation of cardiac output prior to surgery has not been shown to improve patient survival, but if possible pulmonary oedema and sepsis should be treated prior to any run on bypass. Once surgically or catheter-directed correctable causes have been excluded, management is directed to treating ventricular dysfunction.

Haemoptysis

Haemoptysis in this population – particularly those with pulmonary hypertension – should always be considered a serious event, and early transfer to high level care with advanced airway skills immediately available is important. Minor haemoptysis may herald a major bleed, and patients with major haemoptysis usually die due to their unprotected airway rather than blood loss. Haemoptysis in the GUCH population has been attributed to bronchitis, bleeding diathesis, pulmonary arterial rupture, pulmonary embolism, tracheoarterial fistula (in prolonged intubation or tracheostomy) and rupture of aortopulmonary collaterals. In patients with Eisenmenger physiology, haemoptysis accounts for 11–15% of deaths. Investigation will depend upon the skills available locally, but would normally include plain chest radiography, CT angiography and angiography, with a view to embolisation, where it may be life saving.