Pediatric emergency medicine trisk 305
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (104.87 KB, 4 trang )
include drug exposure, congenital heart disease, and WPW syndrome (see
Chapter 86 Cardiac Emergencies ). Approximately 50% of children with
SVT have neither physical findings nor EKG abnormalities between
episodes. In these patients, descriptions of abrupt onset and rapid
termination of palpitations (“like a light switch”) can often be elicited.
VT may also present with palpitations and may be associated with
infections, drug exposure, or even exercise. Infections, especially viral
myocarditis and acute rheumatic fever are some of the most common causes
of acquired VT in children with normal cardiac anatomy. Similarly,
ingestion of drugs that block fast sodium channels and/or potassium
channels (e.g., tricyclic antidepressants, phenothiazines, and antiarrhythmic
agents) is a preventable cause of torsades de pointes (polymorphic VT) and
unstable VT in the otherwise normal child ( Table 63.4 ). Palpitations
associated with exercise may be caused by VT that occurs in conjunction
with hypertrophic cardiomyopathy or myocardial ischemia (see Chapter 86
Cardiac Emergencies ). Patients with the prolonged QT syndrome have a
genetically determined predisposition to fatal VT or have an acquired long
QT syndrome (LQTS) from drugs, hypokalemia, or hypomagnesemia.
LQTS may present with palpitations, presyncope, syncope, cardiac arrest,
and/or seizures (see Chapter 86 Cardiac Emergencies ). Patients who have
undergone ventriculotomy for tetralogy of Fallot comprise another group
who are at high risk for VT as a result of the postoperative development of
scarring in the right ventricular outflow tract. Finally, electrolyte
disturbances,
particularly
hyperkalemia,
hypocalcemia,
and
hypomagnesemia, may be causative in a child with palpitations and VT (see
Chapter 100 Renal and Electrolyte Emergencies ).
TABLE 63.2
COMMON CAUSES OF PALPITATIONS
Exercise
Anxiety/hyperventilation syndrome
Emotional arousal
Drug induced (e.g., caffeine, over-the-counter sympathomimetic agents)
Supraventricular tachycardia
Premature atrial or ventricular contractions
TABLE 63.3
LIFE-THREATENING CAUSES OF PALPITATIONS
Cardiac
Wolff–Parkinson–White syndrome
Prolonged QT syndrome
Hypertrophic cardiomyopathy
Congenital heart disease/postoperative cardiac repair
Myocarditis/acute rheumatic fever
Mitral valve prolapse
Sick sinus syndrome
Complete heart block
Myocardial ischemia
Noncardiac
Hypoxemia
Hypoglycemia
Hyperkalemia
Hypocalcemia
Pheochromocytoma
Poisoning ( Table 63.4 )
Premature atrial contractions produce the most common arrhythmia of
childhood, with 50% of normal children experiencing at least one premature
atrial contraction per day. Premature ventricular contractions (PVCs) also
account for many reports of irregular heartbeat. Although this arrhythmia
can herald serious underlying pathology, patients with an unremarkable
history, normal physical examination, and unifocal PVCs that disappear
with exercise do not require further evaluation. Patients with significant
sinus or AV node dysfunction as a cause of an irregular or slow heartbeat
often have a history of syncope or seizure, slow HR (25 to 50 beats per
minute) on examination, a pulmonic flow murmur, or signs of congestive
heart failure. Patients who have undergone intra-atrial repairs (Dtransposition of the great arteries and atrial septal defect) are at highest risk
for these potentially life-threatening arrhythmias.
TABLE 63.4
DRUGS THAT CAUSE PALPITATIONS/ARRHYTHMIAS
