Cardiac Arrhythmias in Children PDF

Focus on Diagnosis : Cardiac Arrhythmias in Children Eric A. Biondi Pediatrics in Review 2010;31;375 DOI: 10.1542/pir.31-9-375 The online version of this article, along with updated information and services, is...

Focus on Diagnosis : Cardiac Arrhythmias in Children Eric A. Biondi Pediatrics in Review 2010;31;375 DOI: 10.1542/pir.31-9-375 The online version of this article, along with updated information and services, is located on the World Wide Web at: http://pedsinreview.aappublications.org/content/31/9/375 Pediatrics in Review is the official journal of the American Academy of Pediatrics. A monthly publication, it has been published continuously since 1979. Pediatrics in Review is owned, published, and trademarked by the American Academy of Pediatrics, 141 Northwest Point Boulevard, Elk Grove Village, Illinois, 60007. Copyright © 2010 by the American Academy of Pediatrics. All rights reserved. Print ISSN: 0191-9601. Downloaded from http://pedsinreview.aappublications.org/ by Ben Albert on October 15, 2012  focus on diagnosis Cardiac Arrhythmias in Children Eric A. Biondi, MD* Sick Sinus Syndrome Although most significant arrhyth- Introduction mias occur below the SA node, one Although most childhood arrhyth- emanating from the SA node, sick mias are benign, prompt and correct sinus syndrome (SSS), is worth diagnosis of a serious rhythm distur- mentioning briefly. This rhythm is Author Disclosure bance in a child can be lifesaving. a result of SA nodal dysfunction Dr Biondi has disclosed no financial Such rhythm disturbances may arise and is seen most often in patients relationships relevant to this article. at any age and have a wide variety of who had prior cardiac (especially presentations. This article discusses extensive atrial) surgery or cardio- This commentary does not contain a various pediatric arrhythmias that myopathy. Although many forms of discussion of an unapproved/ may be encountered by the commu- SSS are asymptomatic, common clini- investigative use of a commercial cal manifestations include shortness nity pediatrician, highlighting their product/device. presentation, findings on electrocar- of breath, chest pain, and syncope. diography (ECG), and when to refer The rhythm is characterized by for additional evaluation. brady- and tachyarrhythmias. ECG may show SA block, atrial fibrillation The Sinoatrial Node (AF), or supraventricular tachycardia Sinus Rhythm and Sinus (SVT). Patients suspected of having Arrhythmia SSS should be referred to a cardiolo- Some rhythm disturbances originate gist for additional evaluation. within the sinoatrial (SA) node. This cardiac pacemaker is located in the The Atria upper wall of the right atrium and Several common rhythm distur- initiates electrical conduction through bances can arise within the atria. the cardiac muscle. The term sinus ECG findings associated with atrial rhythm designates normal heart rhythms generally involve changes to Abbreviations rhythm controlled by this node. the P wave or P-R interval. AET: atrial ectopic tachycardia ECG shows a P wave with a leftward AF: atrial fibrillation and inferior axis before each QRS Premature Atrial Contractions AP: accessory pathway complex and a normal PR interval Premature atrial contractions (PACs) AV: atrioventricular (120 to 200 msec). are very common in asymptomatic AVNRT: atrioventricular nodal Sinus arrhythmia occurs in pediatric patients and are benign. tachycardia healthy children and is described as They arise when an ectopic focus ECG: electrocardiography a decrease in SA node firing subse- stimulates the atria without input LQTS: long QT syndrome quent to activation of the vagus nerve from the SA node. Although they PAC: premature atrial by exhalation. The heart rate, thus, may be caused by drug use, caffeine, contraction varies with respiration, and ECG or electrolyte imbalances, the incit- PVC: premature ventricular shows sinus rhythm with a prolonga- ing factor usually is unknown. Pa- contraction tion of the R-R interval during ex- tients infrequently report feeling a QTc: corrected QT interval halation. Such prolongation may be “skipped beat” or “pause,” often fol- SA: sinoatrial suppressed with exercise or other lowed by a strong beat, which is the SSS: sick sinus syndrome causes of sinus tachycardia. This find- result of prolonged filling time be- SVT: suptraventricular ing is normal and is not a reason for fore resumption of sinus rhythm. If tachycardia referral. history, physical findings, and ECG VF: ventricular fibrillation are diagnostic, the patient can be re- VT: ventricular tachycardia *Resident in Pediatrics, University of Rochester assured, and no additional evaluation Medical Center, Rochester, NY. is necessary. If the patient is bothered Pediatrics in Review Vol.31 No.9 September 2010 375 Downloaded from http://pedsinreview.aappublications.org/ by Ben Albert on October 15, 2012 focus on diagnosis ally is not life-threatening but can cause palpitations, chest pain, or syn- cope. Careful examination of a pa- tient’s pulse shows an irregularly irreg- ular rhythm. ECG showing absent or very low-voltage P waves and an ir- Figure 1. There is a premature atrial complex (PAC) after the third sinus QRS. Notice regular R-R interval confirms the di- the premature, inverted P wave. The prolonged pause before the next beat suggests agnosis. If AF is suspected but the that the ectopic beat has reset the sinoatrial node. The QRS complex is normal, ECG tracing is normal in the office, indicating that both bundle branches were polarized before the PAC. 24-hour outpatient Holter monitor- ing or the use of event recorders may by PACs, known inciting events children born with structural heart be of assistance. Any patient who has should be avoided. disease, atrial flutter is caused by a the new diagnosis of AF should be Common ECG findings of PACs reentrant circuit confined to the right referred to a pediatric cardiologist. It include premature, inverted, or oddly atrium. Infants may present with is very important to have the patient shaped P waves, indicative of an ec- congestive heart failure, and older seen urgently because prolonged topic atrial focus, and sharp inflec- children may have dizziness, syn- (usually ⬎24 hour) fibrillation or tions, often within the T waves (Fig. cope, chest pain, and shortness of flutter can result in clot development 1). If the premature beat occurs breath. The major clinical clue is the within the left atrium. With resump- while both bundle branches are po- heart rate. In children, atrial flutter tion of sinus rhythm, the clots can larized, it is conducted to both ven- can be conducted to the ventricles embolize, resulting in stroke, myo- tricles simultaneously, resulting in a in a 1:1 fashion, resulting in ventric- cardial damage, or other end-organ normal QRS complex. If one of the ular contractions of more than infarctions. branches is refractory, the beat con- 300 beats/min, or in a ratio of 1:2, ducts along the opposite bundle causing rates of 150 to 200 beats/ branch, resulting in a wide QRS min. In infants, the ECG often shows The Atrioventricular Node complex. Finally, if both ventricles classic inverted “saw-tooth” deflec- and Supraventricular are refractory, the beat is not con- tions, best seen in leads II, III, and Tachycardias ducted and no QRS complex is aVF, that usually are inverted if the Supraventricular Tachycardia formed. This is known as a blocked patient has the typical, counterclock- SVT is defined as a rapid tachycardia PAC. In older patients, such episodes wise reentrant pathway. The patient originating above the bundle of His. are commonly but not invariably should be referred for urgent cardiac It occurs in as many as 1 in 250 suppressed during exercise as a result evaluation and treatment. Neonatal children but often is misdiagnosed of the sinus tachycardia. Referral to a atrial flutter rarely reoccurs after si- due to the variety of presentations pediatric cardiologist is unnecessary. nus rhythm is restored. It is im- it may cause. There are many differ- It is important to remember that portant to note that atypical atrial ent mechanisms for SVT, but they although most PACs are benign, flutter, characterized by slower, more can be divided into three major cate- they may occur rarely in infants in a rounded P waves of lower voltage gories: reentrant tachycardia using bigeminal, blocked fashion, causing separated by an isoelectric line, is a an accessory pathway (AP); reentrant feeding intolerance and decreased potentially lethal arrhythmia, usually atrioventricular nodal tachycardia cardiac output because of the slow occurring in the setting of complex (AVNRT), typically seen in adoles- heart rate. These unusual patients heart disease in older children. cents; and atrial ectopic tachycardia should be referred to a pediatric car- AF is uncommon in young chil- (AET). diologist. dren, although there is evidence to In infants, SVT may present with suggest that it is underreported in heart rates of 220 to 270 beats/min. Atrial Flutter and Fibrillation adolescents. The rhythm derives its Infants who experience prolonged Atrial flutter is another relatively name from rapid fibrillation of the SVT may have a history of poor feed- common arrhythmia that is charac- atrial muscle without coordinated ing, pallor, irritability, and lethargy. terized by atrial rates of 250 to contraction and most often is the The arrhythmia often is diagnosed 400 beats/min. Arising in newborns result of structural heart disease caus- after 24 or 48 hours of sustained who have normal hearts and older ing stretching of the atria. AF gener- SVT, when hemodynamic decom- 376 Pediatrics in Review Vol.31 No.9 September 2010 Downloaded from http://pedsinreview.aappublications.org/ by Ben Albert on October 15, 2012  focus on diagnosis pensation arises and congestive heart failure develops. School-age children can verbalize symptoms and, therefore, usually are seen before developing heart failure. They may complain of “beeping in my chest,” heart pounding, chest pain or fullness, shortness of breath, Figure 2. Wolff-Parkinson-White (WPW) syndrome. Delta waves, a wide QRS complex, sweating, or exercise intolerance. and a short P-R interval (here it is 40 msec) are classic ECG findings in WPW syndrome. They almost never experience syn- cope. The tachycardia rate is slower, characteristics differ based on in only a 24- or 48-hour period, usually 180 to 240 beats/min rather whether the antegrade current is event recorders can operate for up than the approximately 220 to carried by the atrioventricular (AV) to 1 month and are activated by the 270 beats/min seen in infants. node or the accessory pathway. If the patient when symptoms occur. The Adolescents experience similar AP carries such a current, as in Wolff- recorded ECG is sent via telephone signs and symptoms as seen with Parkinson-White syndrome (a condi- to a cardiologist for analysis. Electro- school-age children, but they are tion in which an aberrant AP causes physiologic study is the definitive more capable of precise descriptions. pre-excitation of the ventricles), the method of diagnosing the mecha- It is useful to ask the patient to de- classic findings are a shortened PR nism underlying the SVT and is used scribe the heart rate during the epi- interval and “delta waves,” a gradual for identification of the AP, which sodes, which typically last from a few sloping of the R wave caused by the can be treated with radiofrequency seconds to a few hours. History of a ablation. pre-excitation (Fig. 2). If the AV heart rate that is “too fast to count,” node carries the antegrade current, a pounding sensation in the neck, or an abrupt resolution of palpita- ECG shows a narrow complex tachy- The Ventricles cardia and typically lacks obvious P The ventricles comprise the final car- tions, often after vagal maneuvers, is waves. In this case, sharp upward de- diac area in which arrhythmias can helpful. Another clue is the descrip- flections in the T waves, representing develop, and although several dan- tion of a “switch on-switch off” retrograde conduction through the gerous arrhythmias can develop here, tachycardia rather than a pattern of AP, may be seen. this discussion focuses on the ven- progressive acceleration or decelera- In AVNRT, which occurs more tricular disturbances most likely to tion. Occasionally, a school nurse or commonly in older children, heart present to an outpatient office. Two coach will have counted the pulse rates often are slower without visible uncommon but potentially lethal ar- rate. Such findings help to distin- P waves, which are buried within the rhythmias also are mentioned. guish SVT from other common causes of similar symptoms in adoles- QRS complexes, and an initiating cents such as anxiety, stress, caffeine event such as a PAC may be identi- Premature Ventricular consumption, or dehydration, all of fied. Lastly, the ECG in AET may Contractions which cause sinus tachycardia. show a variable heart rate of up to Premature ventricular contractions SVT in infants may be difficult to 330 beats/min with abnormal P (PVCs) are caused by ectopic firings differentiate from sinus tachycardia waves. This form of SVT is important within the ventricle and, although by ECG. SVT usually manifests as a to identify because rates this fast are less common than PACs, may occur narrow complex (⬍80 msec) tachy- poorly tolerated and affected patients in as many as 25% of healthy children. cardia with a nonvariable heart rate can develop a cardiomyopathy. Patients usually are asymptomatic greater than 220 beats/min. P waves When a patient is suspected of but may report chest fullness, dizzi- often are difficult to see but may be having any form of SVT, cardiac re- ness, or a feeling that the “heart seen as sharp deflections within the T ferral is indicated. Ambulatory ECG skips” and then resumes with a waves. monitoring devices (Holter monitors strong beat. In older children, ECG findings or event recorders) are useful for di- Twelve-lead ECG always should vary, based on the mechanism of agnosing SVT in patients who have be obtained in a patient suspected the SVT. In patients who have AP- sporadic episodes. Compared with of having PVCs to allow the clinician mediated reentry tachycardia, ECG Holter monitors that capture events to assess PVC morphology. Holter Pediatrics in Review Vol.31 No.9 September 2010 377 Downloaded from http://pedsinreview.aappublications.org/ by Ben Albert on October 15, 2012 focus on diagnosis Ventricular Tachycardia Ventricular tachycardia (VT) in chil- dren is defined as a tachycardia of at least three successive ventricular beats. It is referred to as nonsus- tained if the rhythm lasts less than Figure 3. Ventricular bigeminy with premature ventricular beats (PVCs) occurring after 30 seconds and terminates spontane- each sinus beat. The PVCs are uniform, are bizarre, demonstrate wide QRS complexes ously. If it lasts longer than 30 sec- without a preceding P wave, and show T-wave inversion. There is also a prolonged onds, it is considered sustained and pause after each PVC. usually requires therapeutic interven- tion. VT in the pediatric population or event monitoring may be useful interval of more than 450 msec is occurs most commonly in children in documenting infrequent episodes. suggestive of LQTS and more than who have abnormal hearts. Although The PVC itself appears as a prema- 470 msec is considered abnormal many patients are asymptomatic, ture, bizarre, wide QRS complex not (Fig. 4). Using the QTc, calcu- symptoms such as pallor, fatigue, and preceded by a P wave and often fol- lated as the QT interval divided by chest palpitations may occur. In in- lowed by a compensatory pause (Fig. the square root of the previous R-R fants, VT often manifests as feeding 3). The pause is associated with in- interval, is important because that intolerance. Among children who creased ventricular filling and in- value “corrects” the QT interval for have healthy hearts, VT carries a creased stroke volume of the next the patient’s heart rate. There is good prognosis, in contrast to VT in beat that may be noticed by the pa- often a family history of unexplained children who have abnormal hearts tient as a pause followed by a strong sudden death (50% in symptom- or a history of cardiac dysrhythmias. beat. If the PVC occurs close enough atic patients). Patients can present Causative factors include use of to the next sinus beat, a fusion beat with syncope, seizures, palpitations, drugs, caffeine, and decongestants as may occur that has characteristics of and cardiac arrest. As many as 10% well as electrolyte imbalances and both a PVC and a normal QRS com- have episodes of sudden death. Fre- underlying cardiac disease. plex. If they are frequent, PVCs may quently, a previously healthy patient On physical examination, there occur with every other beat (bigem- reports fainting spells while swim- may be evidence of unsuspected con- iny) or every third beat (trigeminy). ming, playing sports, or exercising. genital or acquired cardiac disease. PVCs are benign if they are single, Several genetic cases of LQTS have ECG shows a bizarre, wide QRS uniform in appearance, and sup- been identified. Specifically asking complex (⬎120 msec) tachycardia, pressed or at least not aggravated by about congenital deafness in the fam- which usually has a regular rhythm exercise and there is no evidence of ily can provide a clue to the diagnosis (Fig. 5). P waves may or may not be underlying heart disease or family because deafness often is associated recognizable, depending on the ven- history of sudden, early death. For with a particularly malignant form of tricular rate, and T waves typically are patients who have abnormal family hereditary LQTS. Any patient who opposite in polarization to the QRS. histories, the clinician should be has symptoms and even a borderline The QRS complexes may vary in more suspicious of the potential for prolonged QTc should be referred to appearance if the ectopic input is dangerous ventricular arrhythmias, a pediatric cardiologist. multifocal. Any patient identified as and those patients should be referred to a pediatric cardiologist for addi- tional evaluation. Long QTc Syndrome The long QT syndrome (LQTS) is associated with a potentially danger- Figure 4. Long QT syndrome. The interval from the Q wave to the time at which the ous ventricular arrhythmia, torsades T wave returns to the isoelectric point is prolonged. This ECG also demonstrates sinus de pointes. Although not every pa- arrhythmia, a normal finding, with prolongation of the R-R interval during exhalation. tient who has a prolonged corrected To calculate the corrected QT (QTc) interval, the formula QT/公 previous R-R is used. QT interval (QTc) has LQTS, an The corrected QT interval (QTc) here is 505 msec. (48/公90) 378 Pediatrics in Review Vol.31 No.9 September 2010 Downloaded from http://pedsinreview.aappublications.org/ by Ben Albert on October 15, 2012  focus on diagnosis tive congenital heart disease is in- creasing, it is important to have at least a cursory knowledge of the acute diagnosis and management of VF. Figure 5. Ventricular tachycardia. The heart rate is approximately 200 beats/min, and the QRS complexes are wide (>120 msec). The QRS complexes vary in appearance, suggesting multifocal ectopic input. Summary As in many aspects of medicine, having VT should be assessed imme- bizarre, random waveform without a thorough history is vital for identification and diagnosis of diately for hemodynamic instability. clearly identifiable P waves or QRS cardiac arrhythmias in children Once clinically stable, such patients complexes and a roaming baseline. and can help differentiate a require a cardiac evaluation, includ- Any patient suspected of having VF benign arrhythmia from a ing radiography, echocardiography, requires advanced cardiac life sup- pathologic one. exercise stress testing, and 24-hour port intervention because circulation In most cases, ECG is satisfactory for diagnosis. Holter monitoring. may cease within seconds of onset. In However, if the pediatrician the acute setting, such treatment in- feels that ECG is insufficient, it Ventricular Fibrillation volves the use of an electric defibril- is best to refer the patient to a Ventricular fibrillation (VF) is a rare lator. cardiologist for further cardiac emergency caused by unco- Although many clinicians may go evaluation. ordinated activity of the cardiac mus- an entire career without seeing an cle fibers, often resulting in cardiac episode of VF, its rarity makes it all arrest. The heart tremors rather than the more dangerous. Because this ar- ACKNOWLEDGMENT. I would like contracts and, therefore, pulses are rhythmia occurs most commonly in to thank Dr J. Peter Harris for his nonpalpable. The confirmatory diag- children after heart surgery, and the guidance and support in the writing nostic test is ECG, which shows a number of children surviving opera- of this article. Pediatrics in Review Vol.31 No.9 September 2010 379 Downloaded from http://pedsinreview.aappublications.org/ by Ben Albert on October 15, 2012  Focus on Diagnosis : Cardiac Arrhythmias in Children Eric A. Biondi Pediatrics in Review 2010;31;375 DOI: 10.1542/pir.31-9-375 Updated Information & including high resolution figures, can be found at: Services http://pedsinreview.aappublications.org/content/31/9/375 Subspecialty Collections This article, along with others on similar topics, appears in the following collection(s): Cardiovascular Disorders http://pedsinreview.aappublications.org/cgi/collection/cardiovas cular_disorders Permissions & Licensing Information about reproducing this article in parts (figures, tables) or in its entirety can be found online at: /site/misc/Permissions.xhtml Reprints Information about ordering reprints can be found online: /site/misc/reprints.xhtml Downloaded from http://pedsinreview.aappublications.org/ by Ben Albert on October 15, 2012