Student ECG Cardiac Rhythms 1
SUPRAVENTRICULAR RHYTHMS Rhythms originating in the sinus node, atria, or AV node 2
Rhythms Contents SUPRAVENTRICULAR Normal Sinus Rhythm 6 Sinus Tachycardia 7 Sinus Bradycardia 7 Sinus Arrhythmia 8 Ectopic Atrial Rhythm 10 Wandering Atrial Pacemaker 13 Multifocal Atrial Tachycardia 16 VENTRICULAR Idioventricular Rhythm 48 Accelerated Idioventricular Rhythm 50 Ventricular Tachycardia 52 Torsades de Pointes 56 Ventricular Fibrillation 61 Asystole 63 PVCs 64 Pacemaker Rhythms 67 Atrial Flutter 18 Atrial Fibrillation 23 SVT(AVNRT) 29 Junctional Rhythm 36 Wolf Parkinson White 40 PACs 45 3
Sinus Node Rhythms 4
Normal Sinus Rhythm Normal sinus rhythm is the normal heart rhythm characterized by p waves emanating from the sinus node, upright in II, III, and avf, and at a rate from 60 to 100. Under normal circumstances there is slight irregularity due to autonomic fluctuation with respiration. Loss of this variability could signify autonomic dysfunction. 5
Sinus Tachyardia and Bradycardia Sinus tachycardia is defined as a sinus rhythm at a rate greater than 100. It can get as high as 200 bpm with exercise, but otherwise rarely exceeds 150 bpm. Causes are numerous; treatment is aimed at the underlying cause. Sinus bradycardia is a sinus rhythm at a rate less than 60. It may be physiologic, such as during sleep, with highly trained athletes, from numerous medications. In general treatment may be necessary if the heart rate while awake is < 40 or if >40 and the patient has symptoms 6
Sinus Arrhythmia Normally the heart rate accelerates with inspiration and slows with expiration due to autonomic fluctuation. If the irregularity is exaggerated, it is called sinus arrhythmia. In sinus arrhythmia, the P waves are normal, but the rhythm is regularly irregular--this is not uncommon in children and occ. adults. 7
Atrial Rhythms 8
Ectopic Atrial Rhythm The focus of depolarization is somewhere in the atrium, not the sinus node. Therefore the p-wave axis is usually abnormal. On the ECG, P waves are often inverted in II, III, and avf, where they are normally upright, yet they are constant and regular. The PR interval may be short as the focus is often close to the AV node. 9
Ectopic Atrial Rhythm P waves are inverted in II, III, avf, but the PR interval is constant and the rhythm is regular 10
Ectopic Atrial Rhythm Cause: Usually increased automaticity in the atria (Increased spontaneous depolarization). Symptoms: none usually Treatment: none 11
Wandering Atrial Pacemaker In wandering atrial pacemaker, there are differing foci of depolarization in the atrium other than the sinus node. On the ECG the P waves will be of varying morphologies: some pointed, double peaked, inverted, etc. There should be at least 3 different morphologies apparent. Because of differing distances from the AV node, the P-R intervals will also vary. The rhythm is irregular with a rate less than 100. 12
Wandering Atrial Pacemaker Note differing P waves; rhythm is irregular but rate is less than 100. 13
Wandering Atrial Pacemaker Cause: usually occurs in patients with sinus node dysfunction, atrial abnormalities, increased vagal tone to the SA node, and in normals during sleep. Symptoms: may notice irregular heartbeat, but usually none. Treatment: none; may be transient. 14
Multifocal Atrial Tachycardia MAT is similar to wandering atrial pacemaker, except the rate is above 100 bpm. Sometimes the atrial depolarizations will come early and be blocked due to the refractory period of the AV node. They may also be buried in the prior T wave, causing changes in its morphology. 15
Multifocal Atrial Tachycardia Different P Wave morphologies Very early P wave hidden in T wave 16
Multifocal Atrial Tachycardia MAT is most often seen in patients with severe pulmonary disease (COPD), CHF, especially during exacerbations. Treatment: treat underlying disorder. 17
Atrial Flutter This is usually a reentrant type of arrhythmia that occurs in the atria. Instead of discreet p waves, flutter or F waves are seen, typically at a rate close to 300. They are best seen in leads II, III, avf, and they are conducted to the ventricles at a slower rate due to the longer refractory period of the AV node. Typical conduction is 2:1, 3:1, 4:1, etc. The flutter waves are usually sharp and saw-toothed. 18
Atrial Flutter Saw-toothed flutter waves, best seen in lead II or III 19
What is the rhythm? Same patient: Always look at leads II, III and avf to see P waves more clearly. 20
2 to 1 Atrial Flutter Atrial Rate = 300; Ventricular Rate=150(initially) f f f f f f f The rhythm starts out with a 2:1 atrial flutter, then the ratio changes. Every other flutter wave is buried in a QRS. Atrial flutter may be regular or irregular. 21
Atrial Flutter Symptoms: if ventricular rate fast, may have dyspnea, angina, etc. Treatment: usually AV blocking meds to control ventricular rate if fast, then cardioversion either electrically or by medications. Arrhythmia focus can be ablated by EP cardiologist. 22
Atrial Fibrillation This rhythm results from chaotic random depolarization of the atria. The most common associations are with ischemic, rheumatic, hypertensive heart disease, thyrotoxicosis, heart failure, and aging. 23
Atrial Fibrillation Chaotic, uncoordinated atrial activity on ECG Atrial fibrillation may be coarse, with very visible chaotic atrial activity, or fine, even to the point of almost no baseline activity. The ventricular conduction may be fast or slow, but shows an irregularly irregular pattern. 24
Atrial Fibrillation From coarse(a) to fine(c) QRS complexes QRS complexes 25
Fine Atrial Fibrillation Look closely; sometimes atrial fibrillation is very fine and can be confused with a junctional rhythm. 26
Atrial Fibrillation Symptoms: like atrial flutter if ventricular rate fast. Increased risk of stroke, depending on age, htn, etc. Treatment: rate control, anticoagulation vs conversion to sinus electrically or via medications. 27
AV Nodal Rhythms Supraventricular Tachycardia (AVNRT) Junctional Rhythm Accelerated Junctional Rhythm 28
Supraventricular Tachycardia (SVT) Most are AV nodal reentrant tachycardias (AVNRT), occurring in or around the AV node. Mechanism: when a PAC hits the AV node at the right moment, it can initiate a re-entrant circuit resulting in AVNRT. Usually conduction proceeds down a fast pathway and back up a slow pathway, which has a unidirectional block of antegrade impulses that is variably present. 29
AVNRT Mechanism 1. Atrial Impulse 2. PAC enters 3. Re-entry (PAC) AV Node Fast pathway then recovers and conducts retrograde (final common pathway) Slow Pathway blocked Slow pathway recovers first; fast still refractory 30
AVNRT Less frequently conduction proceeds in the reverse order Reentrant circuits can occur with pathways outside the AV node. 31
SVT (AVNRT) ECG manifestations: Narrow complex regular tachycardia usually > 160 bpm but can be 120-220 P waves may: Be absent (most) Just follow the QRS-often inverted Just precede the QRS(unusual) 32
SVT (AVNRT) Carotid Massage Usual AVNRT with a rapid, narrow complex QRS and no discernable P waves. Conversion to NSR occurs with carotid massage. 33
SVT (AVNRT) Notice the small impulse just after the QRS, which is a retrograde P wave 34
SVT- Treatment Symtoms: palpitations, dyspnea, angina Acute treatment is with vagal maneuvers like carotid massage or valsalva Drug therapy-adenosine, verapamil, beta blockers, sometimes other antiarrhythmics AV nodal ablation is definitive therapy and may be the therapy of choice as meds are only modestly effective. 35
Junctional Rhythm AV nodal tissue can take over as the pacemaker of the heart, especially in the event of sinus node dysfunction. A junctional rhythm is regular, and usually no p waves will be seen. They may be: buried in the QRS complex, occur afterwards during the ST segment, or be superimposed on the T waves. just precede the QRS (rare). 36
Junctional Rhythm 37
Junctional Rhythm The QRS width is narrow as conduction proceeds normally down the bundle branches, and the rate is approx. 40-60. At higher rates, it is referred to as an accelerated junctional rhythm. When the rate is about 120 or greater, it is probably SVT. Junctional rhythm is not re-entry like AVNRT, but is due to failure of the SA node or increased automaticity (accelerated junctional rhythm). Treatment: atropine for JR if HR inadequate. Usually no treatment for accelerated JR. 38
Miscellaneous Supraventricular Rhythms Wolf Parkinson White PACs 39
Wolf-Parkinson-White In WPW there is an accessory bypass tract that directly connects the atrium to the ventricle. It is known as the bundle of Kent, and conducts without the delay seen in the AV node. This is know as pre-excitation. 40
WPW The ECG manifestations are as follows: 1. Short PR interval 2. Delta wave (early abnormal ventricular depolarization). 3. Widened QRS (due to the delta wave). 41
WPW 42
WPW 43
WPW Patients are prone to supraventricular arrhythmias that can conduct rapidly down the accessory pathway at very fast rates leading to ventricular fibrillation and death. This, however, occurs rarely. Definitive treatment is ablation of the accessory pathway. 44
PACs Common extra beats where the atrium depolarizes spontaneously before the next sinus beat should appear. They often have premature and abnormal looking P waves The QRS usually looks like the other QRS complexes. The following R-R interval is usually the same as the sinus beats (or close). 45
PACs Notice the early impulse with the unusual P wave that precedes the QRS. The P wave will be buried in the T wave if the beat comes very early. 46
VENTRICULAR ARRHYTHMIAS 47
Idioventricular Rhythm A focus in the ventricle takes over as the pacemaker of the heart This may be due to failure of pacemaker function from the SA node and AV node. On the ECG there are wide, bizarre QRS complexes at a rate of 20-40, often associated with t-wave inversions. If this rhythm is seen in with a heart block, it is know as a ventricular escape rhythm. 48
Idioventricular Rhythm 49
Accelerated Idioventricular Rhythm (AIVR) Accelerated idioventricular rhythm (AIVR) is a variant of idioventricular rhythm with a rate of 60-100, and often occurs in short bursts after an MI or may be seen with digoxin toxicity. It is from increased automaticity. AIVR is usually transient and benign, and does not carry the same prognosis as ventricular tachycardia. It usually does not require treatment. 50
AIVR in a patient 2 days post MI 51
Ventricular Tachycardia A potentially dangerous rhythm that is often a re-entrant ventricular arrhythmia, arising from a site of abnormal ventricular tissue, often due to ischemia, fibrosis, cardiomyopathy, etc. It also can be precipitated by hypo or hyperkalemia, severe hypocalcemia, hypomagnesemia, severe illness with high catecholamine states, and congenital causes. 52
Ventricular Tachycardia ECG findings: Rapid, wide, bizarre looking QRS complexes at a rate usually above 120-140. The rhythm may be regular or irregular. Sometimes p-waves that are unrelated to the QRS complexes are seen (AV dissociation), usually confirming the diagnosis of v-tach. 53
Ventricular Tachycardia Here, a PVC landing on T wave initiates V Tach 54
Ventricular Tachycardia 55
Ventricular Tachycardia Treatment: If stable, D/C cardioversion, IV amiodarone, occasionally lidocaine. If unstable (severe dyspnea, chest pain, hypotension)-defibrillation. 56
Torsades de Pointes (Twisting of the Points) This is a form of polymorphic ventricular tachycardia that is caused from prolongation of the QT interval (many drugs, low Mg, etc.). On the ECG it looks like v-tach, but the axis shifts 180 degrees, so the complexes shift from positive to negative over several beats. Treatment is with IV magnesium, or pacing to shorten the QT interval. 57
Torsades de Pointes 58
Torsades de Pointes The Axis shifts 180 degrees 59
Torsades de Pointes Treatment: IV Magnesium 2g bolus Defibrillation if sustained/unstable Pacing, isoproterenol to increase HR and shorten QT. 60
Ventricular Fibrillation This is a lethal rhythm resulting from chaotic,random depolarization of the ventricle. It is the usual cause of sudden death. There is an undulating, disorganized rhythm without distinct QRS complexes on the ECG, which may be coarse or fine. Treatment is immediate electrical defibrillation. 61
Ventricular Fibrillation Coarse Fine 62
Asystole No visible electrical actvity Flatline ECG Need to be sure it is not fine v-fib. 63
PVCs Premature ventricular contractions are very common, and may be found in up to 40% of normal individuals. Their prognostic importance depends on the underlying condition and presence of structural heart disease. 64
PVCs On the ECG they appear as early, wide, bizarrelooking complexes with a different morphology than the underlying rhythm. They typically have an abnormal repolarization pattern, often with ST segment depression and T wave inversion. Ventricular bigeminy refers to the pattern of every other beat being a PVC; trigeminy is where every third beat is a PVC. PVCs grouped in 2s are referred to as couplets. 65
PVCs Note the compensatory pause that occurs because the next cycle comes during the PVC or when the ventricle is refractory. 66
Pacemaker-Ventricular The ventricular lead is in the right ventricle, and the resultant complex is wide, often with T wave inversions. Notice the spikes just preceding the QRS. 67
Dual Chamber Pacemaker (a) (v) Note both atrial(a) and ventricular(v) pacing occur, depending on the need. 68
Dual Chamber Pacemaker 69
Supraventricular Arrhythmia Algorithm (use for narrow complex QRS). Is Rhythm Regular Or Irregular? Regular Irregular P Waves Present P Waves Absent (Occasionally follow or precede QRS) P Waves Present P Waves Absent or indiscernable HR<100 HR>100 HR 40-60 HR 80-100 HR>120 HR<100 HR>100 Atrial Fibrillation Flutter Waves Inverted in II, III, avf Upright in II, III, avf Sinus Tachycardia Atrial Tachycardia (P waves may be inverted) Flutter Waves Junctional Rhythm Accelerated Junctional SVT(us AVNRT) P Wave morphology constant P wave morphology changes Flutter Waves Present MAT, Sinus Tach with PACs or PVCs Flutter Waves Present Atrial Flutter Ectopic Atrial Rhythm or Occasional Junctional Normal Sinus/ Sinus Brady Atrial Flutter Sinus dysrhythmia Wandering Atrial Pacemaker, NSR with PACs Atrial Flutter Atrial Flutter 70
Ventricular Arrhythmia Algorithm (Use for Wide Complex QRS) Look at Relationship b/t P Waves and QRS P Waves Absent or unrelated to QRS P Waves Present Before QRS HR <100 HR >100-120 Supraventricular Rhythm with Aberrancy (BBB, etc) Idioventricular (HR 20-40); AIVR if HR 60-100 Complete Heart Block- consider if more P's than QRS Ventricular Tachycardia Ventricular Fibrillation (Chaotic depolarization) Think Torsades if Axis is Shifting 180 Degrees 71