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Bài tập điện tâm đồ nâng cao là bộ gồm hơn 100 bài tập ECG dưới hình thức trắc nghiệm có đáp án và giải thích cơ chế, qua đó sẽ giúp các bạn hiểu rõ hơn về cơ chế trong điện tim, các bạn sẽ cảm thấy thích thú hơn trong việc tiếp cận chúng và giúp ích trong công việc.
7/30/2015 www.medscape.com/viewarticle/841341_print ECG (a concealed PJC). However, this concealed PJC disturbs the AV conduction system such that the sinus beat conducts to the ventricles with a longer PR interval (R5). The same thing happens with R8 (pseudo firstdegree AV block). With P2, the bouncedoff impulse is blocked in the slow pathway and a retrograde P wave (P2) stands alone. Thus, concealed PJCs are doing all kinds of tricks! [1] The R12 and R14 waves are not preexcited because there are no delta waves. Digitalis intoxication is not known to cause the problems seen in the tracing Figure 3 Courtesy of Dr Wang Figure 3 shows all of the potential PQRS relationships with junctional beats. Conduction to the ventricles may occur normally, aberrantly, or not at all depending on the timing of the junctional impulse with the ventricular conduction system [2] Conduction to the atria can have a sinus P wave just before, after, or within the QRS complex with AV dissociation, or a retrograde P wave just before, after, or within the QRS complex, depending upon the timing. Alternatively, only a part of the atria may be conducted from the sinus impulse, and the other part conducted from the junctional impulse, resulting in an atrial fusion. Another possibility: An echo beat, prolonged PR interval (pseudo firstdegree AV block), or concealed junctional beat may cause the sinus P wave to stand alone as if there were a type II seconddegree AV block (pseudo AV block) [1,3] All of these possibilities may seem complicated, but you will agree that they are not! References 1. Wang K. Concealed conduction. In: Atlas of Electrocardiography. Philadelphia, PA: Jaypee Brothers Medical Publishing; 2013:214 2. Wang K. Genesis of aberrant conduction. In: Atlas of Electrocardiography. Philadelphia, PA: Jaypee Brothers Medical Publishing; 2013:112 3. Wang K, Salerno D. Pseudo AV block secondary to concealed premature His bundle depolarizations. Am Heart J 1991;121:12361237 Medscape Cardiology © 2015 WebMD, LLC Cite this article: K. Wang. Are You Tricked by This ECG? Medscape. Mar 26, 2015 http://www.medscape.com/viewarticle/841341_print 2/2 7/30/2015 www.medscape.com/viewarticle/839665_print www.medscape.com What Kind of Block is This? K. Wang, MD February 19, 2015 Figure 1 Courtesy of Dr Wang The P waves and QRS complexes appear unrelated and show which of the following? Complete (thirddegree) AV block Straightforward type I (seconddegree) AV block (AV Wenckebach phenomenon) Type I (seconddegree) AV block and occasional junctional escape beats Save and Proceed Discussion Figure 1 shows straightforward type I (seconddegree) AV block. The QRS complexes do not occur regularly, which immediately rules out thirddegree AV block, because in thirddegree AV block the escape rhythm is very regular, especially if it is junctional (Figure 2) http://www.medscape.com/viewarticle/839665_print 1/2 7/30/2015 www.medscape.com/viewarticle/839665_print Figure 2 Courtesy of Dr Wang As diagrammed in Figure 2, the tracing shows AV Wenckebach phenomenon, where P waves occur regularly, conducting to the ventricles with progressively lengthening PR intervals, until eventually a P wave is blocked. Early on, there was a single 2:1 AV block; a 2:1 AV conduction ratio can be the shortest Wenckebach cycle Ordinarily, the first beat of a Wenckebach cycle has a normal PR interval, but if the AV junction has not fully recovered even after skipping a beat, it could have a long PR interval, as happened in this case. Could those be the junctional escape beats rather than being conducted from the P wave in front of them with a long PR interval? No. The escape beats should occur with the same escape interval, which is not the case here; that is, the first RR interval is longer than the others Medscape Cardiology © 2015 WebMD, LLC Cite this article: What Kind of Block is This? Medscape. Feb 19, 2015 http://www.medscape.com/viewarticle/839665_print 2/2 7/30/2015 www.medscape.com/viewarticle/837353_print www.medscape.com Reversed Arm Leads: Yes or No? K. Wang, MD January 15, 2015 Figure Courtesy of Dr Wang From the findings in lead I, were the left and right arm leads reversed? Yes No Save and Proceed http://www.medscape.com/viewarticle/837353_print 1/2 7/30/2015 www.medscape.com/viewarticle/837353_print Figure Courtesy of Dr Wang Discussion When the QRS complex is entirely inverted in lead l, reversed arm leads come to mind. The first thing that should be checked is the P wave. If it is also inverted, then one is indeed dealing with reversed arm leads or, more rarely, dextrocardia. Here, the P wave is upright, so the arm leads were not misplaced This patient has an extensive anterior myocardial infarction involving the precordial leads as well as leads l and aVL. Thus, a trivial finding such as the P wave direction can, at times, play a decisive role Medscape Cardiology © 2015 WebMD, LLC Cite this article: Reversed Arm Leads: Yes or No? Medscape. Jan 15, 2015 http://www.medscape.com/viewarticle/837353_print 2/2 7/30/2015 www.medscape.com/viewarticle/834372_print www.medscape.com What's the Rhythm? K. Wang, MD November 21, 2014 Review the ECG below and guess which rhythm it depicts Figure 1 What rhythm is shown in Figure 1? Sinus tachycardia Atrial tachycardia Atrial flutter Save and Proceed http://www.medscape.com/viewarticle/834372_print 1/2 7/30/2015 www.medscape.com/viewarticle/834372_print Figure 2 Discussion Regular narrow QRS tachycardia at a rate of 143 bpm is present. A quick glance at the V1 seems to show one P wave in front of each QRS complex, suggestive of sinus or atrial tachycardia. However, there is another blip right after the QRS complex (down arrows in V1 in Figure 2), which is another atrial activity. These atrial activities occur regularly at a rate close to 300 bpm, which is seen only with atrial flutter. So the rhythm is atrial flutter with 2:1 atrioventricular (AV) conduction, whether or not the sawtooth pattern of atrial flutter is seen in the inferior leads If the atrial rate is less than 240 bpm, for example, many other rhythms have to be considered in addition to atrial flutter. In such a case, the sawtooth pattern of atrial flutter must be identified to call it atrial flutter. (The slowest atrial rate in atrial flutter in my collection is 150 bpm.) As illustrated in this case, V1 is very useful in recognizing atrial flutter at times, not because it reveals the sawtooth pattern of atrial flutter but because it may reveal regularly occurring atrial activities at a rate close to 300 bpm In my experience, atrial flutter with 2:1 AV conduction is one of the most misdiagnosed rhythms With the help of the findings in V1, one is more comfortable or convinced of identifying the waves in the rhythm strip of lead II as flutter waves (as drawn) Medscape Cardiology © 2014 WebMD, LLC Cite this article: What's the Rhythm? Medscape. Nov 21, 2014 http://www.medscape.com/viewarticle/834372_print 2/2 7/30/2015 www.medscape.com/viewarticle/831453_print www.medscape.com Why Is Only One PAC Aberrantly Conducted? K. Wang, MD September 15, 2014 Figure. Two premature atrial contractions, indicated by arrows A and B In this tracing, there are two consecutive premature atrial complexes (PACs), "A" and "B" (prematurely occurring beats preceded by prematurely occurring P waves). PAC "A" is aberrantly conducted, whereas PAC "B" is normally conducted Click "next page" to find out why Discussion Because PAC "A" in this tracing is preceded by a longer RR interval than PAC "B," a manifestation of Ashman's phenomenon [13] The length of the refractory period is proportionally related to the preceding RR interval Therefore, the beat preceded by a longer RR interval is more likely to land on the tailend of the refractory period, which now has lengthened, resulting in an aberrant conduction. Dr. Richard Ashman made this observation, and it is now called Ashman's phenomenon The principle of Ashman's phenomenon is useful in determining whether a given wide QRS complex is a ventricular beat in a patient where there are no P waves, such as in atrial fibrillation [1,2] References 1. Wang K. The genesis of aberrant conduction. HQMedEd. September 18, 2013. http://hqmeded.com/the genesisofaberrantconduction/ Accessed September 8, 2014 2. Wang K. Genesis of aberrant conduction. In: Wang K. Atlas of Electrocardiography. Philadelphia, PA: Jaypee http://www.medscape.com/viewarticle/831453_print 1/2 7/30/2015 www.medscape.com/viewarticle/831453_print Brothers Medical Publishing; 2013:124, 161 3. Wang K. Ashman's phenomenon. ECG SelfStudy Book. Philadelphia, PA: Jaypee Brothers Medical Publishing; 2014:27, 155, 224, 259 Medscape Cardiology © 2014 WebMD, LLC Cite this article: Why Is Only One PAC Aberrantly Conducted? Medscape. Sep 15, 2014 http://www.medscape.com/viewarticle/831453_print 2/2 7/30/2015 www.medscape.com/viewarticle/832423_print www.medscape.com Ventricular Preexcitation of Every Other Beat? K. Wang, MD October 15, 2014 Ventricular preexcitation can be intermittent [1,2] Sometimes only every other beat is preexcited, and sometimes several beats are preexcited at a time or for several days at a time. In leads V46 of this case, every other QRS complex is wide and has a short PR interval, and the upstroke is slurred (Figure) Figure This tracing reflects which of the following? Ventricular preexcitation affecting every other beat Ventricular bigeminy Save and Proceed http://www.medscape.com/viewarticle/832423_print 1/2 7/30/2015 www.medscape.com/viewarticle/832423_print Discussion The wide complexes in V46 indeed suggest ventricular preexcitation (short PR interval, slurred upstroke of delta waves). However, observations of the rhythm strips of VI, II, and V5, from right to left, show that the P wave in front of the wide QRS complex gradually marches into the QRS rather than maintaining a fixed relationship. Therefore, these are not ventricular preexcited beats but simply a ventricular bigeminy which happens to have a "pseudo" delta wave [1] Some QRS complexes have a slurred upstroke without being preexcited, which I would call a "pseudo" delta wave [1] References 1. Wang K. Atlas of Electrocardiography. Philadelphia, Pa: Jaypee Brothers Medical Publishing; 2013:200213 2. Wang K. Misleading ventricular preexcitation ECG findings. HQMedEd. May 30, 2013 http://hqmeded.com/misleadingventricularpreexcitationecgfindings2/ Accessed September 21, 2014 Medscape Cardiology © 2014 WebMD, LLC Cite this article: Ventricular Preexcitation of Every Other Beat? Medscape. Oct 15, 2014 http://www.medscape.com/viewarticle/832423_print 2/2 7/30/2015 www.medscape.com/viewarticle/828939_print www.medscape.com Brugada Syndrome Update: More Common Than Imagined Amal Mattu, MD July 31, 2014 Introduction Those who know me know that I love ECGs. I love reading about them, writing about them, and talking about them. A major reason for this infatuation is that the ECG is arguably the most important test in acute care medicine This simple test, which is rapid, lowcost (a piece of paper and ink!) and reproducible and can be done at the bedside in any patient regardless of how sick, can provide lifesaving information. This intense interest has led me to develop several lectures as well as an openaccess, weekly ECG Case of the Week video that I offer to anyone interested in learning more about ECGs Because of this interest and my ECG Website, many physicians in emergency medicine in the United States and abroad send me interesting cases, questions, and quandaries pertaining to ECG. Without a doubt, one of the most common topics on which I receive questions has to do with the Brugada syndrome First identified and described in the early 1990s, the Brugada syndrome has become one of the most intriguing topics that emergency physicians and cardiologists have been learning about in ECG over the past 2 decades. In short, the Brugada syndrome is an abnormality in the electrical system of the heart that predisposes patients to develop episodes of ventricular tachycardia and loss of consciousness. The arrhythmia may spontaneously terminate, after which the patient wakes up and presents for evaluation of syncope; or the arrhythmia may degenerate into ventricular fibrillation, resulting in sudden death The ECG of these patients in the asymptomatic state often shows a characteristic incomplete or complete right bundle branch block pattern with STsegment elevation in leads V1V2 (Figure 1). Definitive testing for Brugada syndrome is done in the electrophysiology laboratory, where, if the diagnosis is confirmed, an implantable cardioverterdefibrillator (ICD) is placed. Without the ICD, mortality from the condition was thought to be as high as 10% per year [1] http://www.medscape.com/viewarticle/828939_print 1/4 7/30/2015 www.medscape.com/viewarticle/828939_print A full review of the topic is beyond of the scope of this brief essay, and any readers who are not familiar with it are referred to any one of the many review articles or videos available via the Internet. However, for those who are familiar with the Brugada syndrome, a review of the most recent literature on this topic is in order. Two recent articles from the electrophysiology literature provide some outstanding updates on diagnosis and risk assessment of these patients [2,3] I will offer some background on this syndrome: • The prevailing theory regarding the pathophysiology of Brugada syndrome is that it is a sodium channelopathy caused by a genetic mutation. Most patients, however, do not appear to have a hereditary pattern of the condition • STsegment elevation in leads V1V2 in these patients comes in 2 varieties (Figure 2): a covedtype (straight or convex upward) terminating in an inverted Twave, and a saddletype (concave upward). The coved type is far more predictive of arrhythmic events • In conjunction with the ECG abnormality, one of the following criteria is also necessary to make the diagnosis: i. A history of ventricular tachycardia or ventricular fibrillation; ii. A family history of sudden cardiac death; iii. A family history of the covedtype ECG abnormality; http://www.medscape.com/viewarticle/828939_print 2/4 7/30/2015 www.medscape.com/viewarticle/828939_print iv. Agonal respirations during sleep; or v. Inducibility of ventricular tachycardia or ventricular fibrillation during electrophysiologic studies • The Brugada ECG pattern is more prominent at night, at rest, and after large meals; this also correlates with when the majority of arrhythmias and sudden death episodes occur • Fever can induce the ECG abnormality as well as arrhythmias • Most sodiumchannel blockers tend to provoke the ECG abnormality. Electrophysiologists typically will use potent sodiumchannel blockers in the electrophysiology laboratory as part of the diagnostic testing for the Brugada syndrome • Brugada syndrome was first identified as a common cause of sudden death in young males of Southeast Asian descent. However, the condition is now well documented in both men and women from many different ethnic groups, and in a large age range of patients • The average age at diagnosis of Brugada syndrome is about 40 years. This contrasts with other heart diseases associated with sudden death, such as hypertrophic cardiomyopathy and long QT syndrome, which typically occur at younger ages. However, arrhythmic events related to Brugada syndrome are reported in patients ranging from 2 days to 84 years of age. The condition is now believed to be one of the potential causes of sudden infant death syndrome and sudden cardiac death in young children • Asymptomatic patients with the Brugada pattern on ECG (ie, an incidental finding of the Brugada pattern) and patients with only a druginduced Brugada pattern appear to have a much lower risk for arrhythmia than previously thought perhaps less than 5% over 34 years • Because of the low annual rate of arrhythmic events in asymptomatic patients and the negative physical and psychological effects of ICDs, the need for ICD placement needs to be very carefully evaluated Viewpoint The electrocardiogram was invented more than 100 years ago. Taking this into account, one realizes that the Brugada syndrome is one of the most recent "discoveries" in electrocardiography, first identified slightly more than 20 years ago When most of us first started hearing about this entity, we assumed that it was a "zebra" disease one that we would probably not encounter and therefore probably didn't need to learn about However, on the basis of the literature that has accumulated worldwide, we've come to learn that the Brugada syndrome is now more common than we ever imagined: It is estimated to account for 4% of all sudden deaths and 20% of sudden deaths in patients without structural heart disease [4] It turns out that we've been missing this diagnosis for many years Brugada syndrome is now considered core knowledge for not only cardiologists, but also emergency physicians. This entity is now routinely discussed at major conferences, in emergency medicine board review courses, and in residency curricula. Diagnoses are routinely being made in emergency departments, and consequently young patients' lives are being saved It is critically important for all acute care physicians to be familiar with the basics as well as the advances regarding Brugada syndrome. This is yet another opportunity for all of us to save lives by properly interpreting a simple test: that piece of paper and ink called the ECG References 1. Mattu A, Rogers RL, Kim H, Perron AD, Brady WJ. The Brugada syndrome. Am J Emerg Med. 2003;21:146 http://www.medscape.com/viewarticle/828939_print 3/4 7/30/2015 www.medscape.com/viewarticle/828939_print 151. Abstract 2. Mizusawa Y, Wilde AA. Brugada syndrome. Circ Arrhythm Electrophysiol. 2012;5:606616. Abstract 3. Hoogendijk MG, Opthof T, Postema PG, Wilde AA, de Bakker JM, Coronel R. The Brugada ECG pattern: a marker of channelopathy, structural heart disease, or neither? Toward a unifying mechanism of the Brugada syndrome. Circ Arrhythm Electrophysiol. 2010;3:283290. Abstract 4. Antzelevitch C, Brugada P, Borggrefe M, et al. Brugada syndrome: report of the Second Consensus Conference: endorsed by the Heart Rhythm Society and the European Heart Rhythm Association. Circulation 2005;111:659670. Abstract Medscape Emergency Medicine © 2014 WebMD, LLC Cite this article: Brugada Syndrome Update: More Common Than Imagined. Medscape. Jul 31, 2014 http://www.medscape.com/viewarticle/828939_print 4/4