Cardiac catheterization is performed in patients who needadditional anatomic information or precise hemodynamicinformation before operating or establishing a managementplan. Pressures, oxygen saturations, and oxygen content aremeasured in each chamber and blood vessel entered (Fig. 139-5). This information is used to calculate systemic andpulmonary blood flow and resistance. Angiography is performed by injecting contrast material into selected sites to define anatomy and supplement noninvasive information.An increasing percentage of cardiac catheterizations are doneto perform an intervention, including balloon dilation of stenotic valves and vessels, ballooning and stenting of stenoticlesions, closure of collateral vessels by coil embolization, anddevice closure of PDAs, secundum ASDs, patent foramen ovales, and muscular VSDs. Catheterization with electro-physiologic studies allows for precise mapping of the electrical activity, can assess the risk of abnormal heart rhythms,and often is done in anticipation of radiofrequency ablationof the site of a dysrhythmia.
Figure 139-5 The normal heart. AO, Aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle. Circled values are oxygen saturations.
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Syncope is the transient loss of consciousness and muscle tone that, by history, does not suggest other altered states of consciousness. Presyncope or near-syncope has many or all of the prodromal symptoms without loss of consciousness. Syncope is relatively common (Table 140-1). The frequency of episodes, amount of stress, and functional impairment caused by syncope vary. Most syncopal events are relatively benign, but can represent a serious cardiac condition that may lead to death (Table 140-1). The differential diagnosis for typical syncope includes seizure, metabolic cause (hypoglycemia), hyperventilation, atypical migraine, and breath holding.
Typical syncopal events usually occur in the upright position or are related to changing position. Syncope may be associated with anxiety, pain, blood drawing or the sight of blood, fasting, a hot environment, or crowded places. The patient often appears pale. A prodrome, consisting of dizziness, lightheadedness, nausea, diaphoresis, visual changes (blacking out), or possibly palpitations, warns the patient and often prevents
Table 140-1 Syncope and Dizziness: Etiology DIAGNOSIS HISTORY SIGNS/ SYMPTOMS DESCRIPTION HEART RATE/ BLOOD PRESSURE DURATION POSTSYNCOPE RECURRENCE Neurocardiogenic (vasodepressor) At rest Pallor, nausea, visual changes Brief ± convulsion ↓/↓<1 min Residual pallor, sweaty, hot; recurs Common
Micturition Postvoiding Pallor, nausea Brief; ↓/↓ < 1 min
Carotid sinus Tight collar, Vague, visual Sudden onset, Usually ↓/↓ <5 min Fatigue or (+) turned head changes pallor
Tumor or mass Recumbent, SOB ± chest Pallor ↑/↓ Any duration Baseline (+) paroxysmal pain
Coronary artery Exercise SOB ± chest Pallor ↑/↓ Any duration Fatigue, chest (+) disease
From Lewis DA: Syncope and dizziness. In Kliegman RM, editor: Practical Strategies in Pediatric Diagnosis and Therapy, Philadelphia, 1996, WB Saunders. LVOT, Left ventricular outflow tract; SOB, shortness of breath; ±, with or without; (+), yes but not consistent or predictable.
injury. Unconsciousness lasts for less than 1 minute. A return to normal consciousness occurs relatively quickly. Most of these syncopal episodes are vasovagal or neurocardiogenic in origin. The physical examination is normal.