Cardiophile MD Archive » ECG

SVT with RBBB

Johnson Francis — Mon, 24 May 2010 07:43:47 +0000

Supraventricular tachycardia with RBBB pattern

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Supraventricular tachycardia with RBBB pattern as evidenced by the slurred S wave in lead I and aVL and rSR’ pattern in V1. The right bundle conduction is slower during tachycardia and hence right bundle aberrancy is more likely to occur than left bundle aberrancy. It could also be a pre-existing right bundle branch block. In this case the person had Ebstein’s anomaly of tricuspid valve. Ebstein’s anomaly can be associated with RBBB pattern or polyphasic QRS complexes. They can also have right sided accessory pathways which can predispose to atrioventricular re-entrant tachycardia.

IRBB and LVH

Johnson Francis — Sun, 16 May 2010 05:13:47 +0000

Incomplete right bundle branch block and left ventricular hypertrophy

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Incomplete right bundle branch block (IRBBB) is manifested as a rsr’ pattern in leads V1 and V2 (C1 and C2 in the image), with T wave inversion in the anterior leads V1 to V5. Left ventricular hypertrophy (LVH) is manifest as tall R waves in lateral leads which are partly overlapped by the deep S waves in the tracing in the channel above. Those deep S waves indicate an element of associated right ventricular hypertrophy. In fact there was a large ventricular septal defect and double outlet left ventricle with severe pulmonary hypertension in this person, explaining the biventricular hypertrophy.

Complex ventricular ectopy

Johnson Francis — Sun, 02 May 2010 17:12:57 +0000

Complex ventricular ectopy

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Multiple wide bizarre QRS complexes without preceding P waves are ventricular ectopic beats. Since they have different morphologies, they are unlikely to be amenable for radiofrequency catheter ablation. Some of the couplets are seen to be bidirectional while others are unidirectional. In addition, there are QS complexes in V1 and V2 with a slightly coved ST segment and T wave inversion, reminiscent of an old myocardial infarction. Such complex ventricular ectopy occurring frequently over a long period of the order of a decade can predispose to tachycardiomyopathy. On the other hand the ectopy can be an association of familial dilated cardiomyopathy.

Electrical alternans

Johnson Francis — Fri, 19 Mar 2010 09:14:32 +0000

Electrical alternans is a phenomenon seen on the electrocardiogram with alternation in the amplitude of QRS complexes. The term electrical alternans totalis is used when the amplitudes of all the waves (P, QRS and T) show alternating amplitude. Electrical alternans totalis is seen in cardiac tamponade and is thought to be due to the heart swinging movement of the heart within the pericardial cavity. Electrical alternans may sometimes be associated with its mechanical counter part: pulsus alternans. But most often the two are unrelated. Another situation in which electrical alternans is seen is with supraventicular ectopic bigeminy. The ectopic beat often has a lower QRS amplitude, possibly due to the lower ventricular volume at the onset of systole (Brody’s effect).

Isolated alternans of the ST segment and T wave also may occur. T wave alternans can be macroscopic or microvolt T wave alternans which can be detected only with special equipment. ST segment and T wave alternans have been reported in vasospastic angina and is thought to be the harbringer of life threatening arrhythmias. T wave alternans (both macroscopic and microvolt) have also been linked with ventricular arrhythmias and sudden cardiac death. T wave alternans has been noted in congenital long QT syndrome preceding torsades des pointes.

Second degree AV block

Johnson Francis — Wed, 24 Feb 2010 07:56:36 +0000

Second degree AV block

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There is a limitation in interpreting the rhythm as a long rhythm strip is not available. This is often the situation when the ECG is obtained without your supervision. The PR interval of the first beat is quite prolonged so that it overlaps with the T wave of the previous beat. The next P wave is superimposed on the T wave as well as non conducted, resulting in a pause. The PR interval of the second beat is less prolonged as the conduction recovers partially following the blocked beat and the pause. The next PR interval is again prolonged. So overall the ECG shows a 3:2 type I AV block. QRS complex is narrow, indicating a supra Hisean location of the block. These features fit in with the Wenckebach phenomenon.

VPC couplet

Johnson Francis — Thu, 18 Feb 2010 08:58:44 +0000

Ventricular premature complexes (VPCs) in couplet

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Ventricular premature complexes seen as wide bizarre QRS complexes not preceded by a P wave. Initial two VPCs are isolated while the last two occur in rapid sequence as a couplet. Couplets may be a forerunner of ventricular tachycardia. Isolated VPCs and the couplet are followed by a compensatory pause. All the VPCs have same morphology (monmorphic) indicating the same focus of origin (unifocal). Unifocal VPCs usually have the same coupling interval. Coupling interval is the interval from the onset of the preceding sinus beat to the onset of the ectopic beat. Unifocal VPCs from a parasystolic focus can have varying coupling interval. Parasystolic focus is a protected focus with entrance block. It captures the ventricle whenever it finds that the ventricle is not refractory from a conducted beat. The interectopic intervals in a parasystole have a common denominator.

Pacemapping of arrhythmias

Johnson Francis — Sun, 31 Jan 2010 16:45:56 +0000

The two common methods of mapping cardiac arrhythmias are activation mapping and pacemapping. In activation mapping, spontaneous or induced tachycardia is mapped to detected the earliest activation site, which is targeted for ablation. When the tachycardia is difficult to induce, pacemapping is useful. It can also corroborate the findings of activation mapping. Pacemapping at potential ablation sites is done at a rate slightly faster than the ventricular tachycardia. The QRS morphology should be a 12/12 match of the clinical tachycardia or ventricular premature complexes. It should be an exact replica including any small notches, indicating that the stimulation is being performed at the exact site of the ectopic impulse formation. Ablation from such perfect pacemap sites are usually successful. But when the match is less (e.g. 10/12 lead match), the chance of success is less. As little current as needed to reliably capture is to be used for pacemapping. If the current needed for capture is more than 5 mA, the electrode contact is poor and needs adjustment.

Catheter induced ectopy

Johnson Francis — Sun, 31 Jan 2010 14:24:27 +0000

Catheter induced ectopy is due to irritation of the local endocardium and will show all the features of a target ventricular ectopic for ablation: QS complexes in unipolar recordings, onset of QRS in the unipolar distal lead and the bipolar distal lead of the ablation catheter preceding the QRS in other leads. But this site should not be targeted for ablation. Only spontaneously occurring ectopics with the same features should be targeted for ablation.

Catheter induced ectopy also causes problem in interpreting mitral regurgitation. While taking a left ventriculogram to assess mitral regurgitation, the catheter should be in the mid cavity to avoid ectopy as far as possible.

Catheter induced ectopy is sometimes useful to terminate a tachycardia which occurs in the course of an electrophysiological study or a cath study.

Post ectopic potentiation is another phenomenon which can be associated with catheter induced ectopy, just like any other ectopy.

ST elevation during treadmill test

Johnson Francis — Sun, 31 Jan 2010 08:49:27 +0000

Usual ischemic response on a treadmill ECG is ST segment depression. But sometimes ST segment elevation may also be noted. ST segment depression seen during treadmill test (TMT) does not have localizing value regarding the territory of ischemia. But ST elevation is thought to have localizing value. ST segment elevation occurring in leads with Q waves was initially thought not to represent ischemia and rather a manifestation of a dyskinetic segment. But now ST segment elevation in leads with Q waves is thought to be a sign of viability in the infarct territory. In this series, there is ST segment elevation in the inferior leads with Q waves as well as ST depression in I and aVL, persisting well into recovery. In some cases during treadmill test, ST segment depression does not appear during exercise, but only in recovery. In still others, ST segment depression is mild and horizontal during the exercise, but worsens in recovery, often becoming downsloping. All these changes are quite significant and are considered indications for coronary angiography.

TMT stage 1 showing ST elevation in inferior leads and ST depression in lead I and II

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TMT stage 2 showing ST elevation in inferior leads and ST depression in lead I and II

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TMT stage 3 showing ST elevation in inferior leads and ST depression in lead I and II

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TMT recovery at 2 minutes showing ST elevation in inferior leads and mild ST depression in lead I and II

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TMT recovery at 6 minutes showing ST elevation in inferior leads and mild ST depression in lead I and II

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Sinus bradycardia with first degree AV block

Johnson Francis — Sun, 31 Jan 2010 08:35:31 +0000

Sinus bradycardia with first degree AV block

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Sinus bradycardia is evident from the long RR interval of 1280 msec, corresponding to a heart rate of 47 per minute. PR interval is also prolonged at about 320 msec. The combination can occur in vagotonic states or in those on betablockers or other drugs which suppress both the sinus node and the AV node. Pure sinus node inhibitors like ivabradine cannot produce this combination. This combination is also often seen with acute inferior wall myocardial infarction.