All anesthetic agents can affect the normal cardiovascular system profoundly and adversely. The sinus node, conduction system, and myocardial contractility all can be depressed by general anesthetics. Moreover, these drugs alter both preload and afterload by relaxing vascular smooth-muscle tone. General anesthetics also attenuate hypoxic pulmonary vasoconstriction and thereby impair ventilation perfusion matching. The combination of vasodilatation and impaired myocardial contractility often causes some degree of hypotension, especially in children who are relatively hypovolemic because of a prolonged fast or excessive fluid loss (eg, diarrhea, vomiting, hemorrhage). Because the presence of underlying heart disease increases the inherent risks of anesthesia, the preanesthetic cardiac evaluation should identify whether cardiac dysfunction, structural heart disease, or hypertension is present and whether subacute bacterial endocarditis (SBE) prophylaxis is needed.

Many children will have heart murmurs noted during their preanesthetic evaluation. Does a child with a heart murmur need a cardiology evaluation? Given the high prevalence (75% to 90%) of innocent murmurs through childhood, most children will have an audible murmur at some point; however, most of these children will not require a cardiology consultation.[77] Innocent murmurs are frequently episodic in appearance and are associated with a normally split second heart sound, normal exercise tolerance, and a normal electrocardiogram. The 3 most common murmurs are the Still's murmur, the innocent pulmonary murmur, and the arterial supraclavicular bruit. The defining characteristics of the innocent murmurs are summarized in Table 62-3.

Still's murmur is most frequent in late preschool and is exacerbated by fever, exercise, and anemia.[78] Still's murmur is low pitched and decreases with standing, which distinguishes it from a small ventricular septal defect and hypertrophic obstructive cardiomyopathy.[79] The innocent pulmonary murmur is most common during middle to late childhood and can appear during febrile illnesses, anemia, and pregnancy. A normal split second heart sound differentiates the innocent pulmonary murmur from an atrial septal defect, as well as pulmonary valvular disease.[80]

Alternatively, cardiac murmurs can be indicative of either intracardiac shunts or valvular heart disease. Because anesthetic agents have varying degrees of effects on pulmonary and systemic vascular resistance, heart rate, and contractility, an inappropriate choice of anesthetic agent can severely disturb a previously balanced pathophysiological state. For this reason, all murmurs of questionable status should be evaluated by a pediatric cardiologist, and all pathologic findings should be communicated directly to the pediatric anesthesiologist.

A newly diagnosed murmur can represent underlying congenital heart disease with intracardiac shunts or unappreciated valvular heart disease, both of which may require SBE prophylaxis. Cardiology consultation is warranted when this new murmur does not appear to be innocent or is associated with changes in exercise tolerance, respiratory status, or perfusion.

Children with congenital heart disease (whether repaired or not) should have a cardiac evaluation within 1 year before surgery, even if asymptomatic. Current use of cardiac medications, prolonged QT syndrome and residual cardiac disease all disqualify a child from having procedures performed at freestanding ambulatory surgical facilities.

	Location	Quality	Increased By	Decreased By
Still's murmur	LLSB without radiation	Low pitch vibratory	Exercise	Standing
Pulmonary murmur	LUSB	Blowing midsystolic	Expiration	Standing
Supraclavicular bruit	R supraclavicular fossa	Harsh systolic ejection	Pressure	Shoulder extension

LLSB, Left lower sternal border; LUSB, left upper sternal border.

Williams syndrome is a constellation of dysmorphic facies, intellectual disability, growth deficiency, neonatal hypercalcemia, genitourinary anomalies, and congenital heart disease.[81] The principal cardiac manifestation is supravalvular aortic stenosis, which is often progressive. Other end-organ manifestations of Williams syndrome include epilepsy, persistent hypercalcemia, hypothyroidism, renovascular hypertension, and proteinuria.[82] The locus for the deletion responsible for this syndrome is in the ELN gene on chromosome 7, which codes for elastin.[83]

A reduced amount of elastin in the media of the aorta is thought to produce aortic narrowing at the sinotubular junction producing the supravalvular aortic stenosis; a similar process can occur in any artery.[84] Pulmonary arterial obstruction is seen in 80% of cases.[85] Sudden death is estimated to occur in at least 3% of patients with Williams syndrome; many deaths occur during the perioperative period.[86] At postmortem examination, coronary artery stenosis, and biventricular outflow tract obstruction have been identified and are thought to contribute to myocardial ischemia, decreased cardiac output, and ventricular dysrhythmias. The coronary artery stenosis may be caused by ostia obstruction from the distorted aortic valve or by abnormalities in elastin production. Retrospectively, many of these patients had evidence of myocardial ischemia on preoperative electrocardiogram or Holter monitor.[87]

Patients with Williams syndrome should be considered at high risk for perioperative complications. Given that their cardiac disease appears to be dynamic, a thorough history looking for a change in exercise tolerance, dyspnea, angina, and syncope should be sought. A complete cardiologic evaluation, including an echocardiogram, should be performed before the administration of each anesthetic, looking for evidence of outflow tract obstruction, coronary artery anomalies, and segmental wall motion abnormalities, suggestive of myocardial ischemia. Anesthetic induction must be performed with great care, avoiding extremes in heart rate and blood pressure.

Prolonged (or long) QT syndrome (LQTS) is the perturbation of ion channels impairing ventricular repolarization, which puts patients at increased risk for Torsades de pointes, a polymorphic ventricular tachycardia. Prolongation of the QT segment results from either congenital genetic mutations or the effects of drugs or metabolic abnormalities on the ion channels responsible for repolarization (Table 62-4). Congenital LQTS can occur in children at any age. The prevalence is 1 in 5000 persons.[88] [89] Most of the genetic mutations are inherited in an autosomal-dominant manner. Far less common is the autosomal-recessive LQTS and sensorineural deafness, affecting 1 in 1 million people.[90] These patients present with syncope, seizures, or sudden cardiac death after an increase in sympathetic activity, commonly in the form of exercise, an auditory stimulus, or emotional stress.

A preoperative electrocardiographic evaluation should be performed on children with a history of any these manifestations, who have a family history of sudden death, or who are receiving long-term administration of one of the drugs listed in Table 62-4, looking for a QT_c greater than 470 ms in male patients and 480 ms in female patients. Only 60% of patients are symptomatic at the time of recognition.[91] Children with LQTS should have electrolytes measured to ensure that serum levels of potassium, calcium, and magnesium are normal. Patients with a risk of congenital LQTS should avoid all of the drugs listed in Table 62-4, if possible. Potent anesthetic vapors have effects on the cardiac conduction system and should be used in these patients with great care.[92]

Generic Name	Brand Name	Category*
Albuterol	Ventolin, Proventil	3
Amantadine	Symmetrel	2
Amiodarone	Pacerone, Cordarone	1
Amphetamine/dextroamphetamine	Adderall	3
Atomoxetine	Strattera	3
Azithromycin	Zithromax	2
Chloral hydrate	Noctec	2
Chloroquine	Arelan	1
Chlorpromazine	Thorazine	1
Clarithromycin	Biaxin	1
Clozapine	Clozaril	2
Dextroamphetamine	Dexadrine	3
Disopyramide	Norpace	1
Dobutamine	Dobutrex	3
Dolasetron	Anzemet	2
Dopamine	Intropin	3
Droperidol	Inapsine	1
Ephedrine	Rumatuss	3
Epinephrine	Primatene, Bronkaid	3
Erythromycin	Erythrocin , EES	1
Felbamate	Felbatrol	2
Flecainide	Tambocor	2
Foscarnet	Foscavir	2
Fosphenytoin	Cerebyx	2
Gemifloxacin	Factive	2
Granisetron	Kytril	2
Halofantrine	Halfan	1
Haloperidol	Haldol	1
Isoproterenol	Isupres, Medihaler-Iso	3
Isradipine	Dynacirc	2
Levalbuterol	Xopenex	3
Levofloxacin	Levaquin	2
Lithium	Lithobid, Eskalith	2
Metaproterenol	Alupent, Metaprel	3
Methadone	Dolophine, Methadose	1
Methylphenidate	Ritalin , Concerta	3
Milodrine	ProAmantine	3
Moxifloxacin	Avelox	2
Nicardipine	Cardene	2
Norepinephrine	Levophed	3
Octreotide	Sandostatin	2
Ofloxacin	Floxin	2
Ondansetron	Zofran	2
Pentamidine	Pentam, NebuPent	1
Phenylephrine	Neosynephrine	3
Pimozide	Orap	1
Procainamide	Pronestyl	1
Pseudoephedrine	PediaCare, Sudafed	3
Quetiapine	Seroquel	2
Quinidine	Quinaglute, Cardioquin	1
Risperidone	Risperdal	2
Salmeterol	Serevent	3
Sotalol	Betapace	1
Tacrolimus	Prograf	2
Telithromycin	Ketek	2
Terbutaline	Brethine	3
Thioridazine	Mellaril	1
Tizanidine	Zanaflex	2
Venlafaxine	Effexor	2
Ziprasidone	Geodon	2

Drugs in bold type are commonly used in perioperative period.
Drugs in italics type are commonly used in children.
^*Category 1: Drugs that are generally accepted by authorities to have a risk of prolonging the QT interval and causing Torsades de pointes.
Category 2: Drugs that may prolong the QT interval but at this time lack substantial evidence for causing Torsades de pointes.
Category 3: Drugs to be avoided for use in patients with diagnosed or suspected congenital long QT syndrome (in addition to drugs in categories 1 and 2).
A continuously updated and complete list of drugs that prolong QT, as well a list of drugs which do not prolong QT and are therefore safe in patients with long QT, may be found at www.torsades.org/medical-pros/drug-lists/drug-lists.htm#. (Accessed July 21, 2006.)