Carolinas Emergency Medicine Residency

The significance of Respiratory artifact (RA) in the ECG - Dr. Littmann

5/5/2016

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I. Characteristics of respiratory artifact

Repetitive microoscillations, best seen in the inferolateral leads; rarely seen in leads I and V1
Occasionally, the microoscillations are preceded by what look like P waves - the presence of pseudo-P waves may mimic atrial dissociation
The RA corresponds to the inspiratory phase of the respiratory cycle
Duration of the RA corresponds to duration of the inspiratory phase of respiration

II. The clinical significance of respiratory artifact

The presence of RA always indicates increased work of breathing, respiratory distress
It allows precise measurement and tracking of the respiratory rate - count the number of RAs in the 10-sec 12-lead ECG and multiply it by 6; measure 1 or more respiratory cycles in mm and divide it into 1,500 or its multiples
44% of pts with RA required ventilation support; 28% required intubation, mechanical ventilation
Successful treatment of the underlying condition resulted in a decreased rate or elimination of RA

III. Respiratory artifact can aid in the recognition of sleep-disordered breathing

Central sleep apnea is characterized by

a. marked sinus deceleration or AV block followed by
b. an abrupt increase in heart rate and the
c. simultaneous appearance of very fast RA

Obstructive sleep apnea is characterized by

a. profound sinus bradycardia with
b. simultaneously occurring very long respiratory (snoring) artifact followed by
c. a sudden increase in the heart rate and resolution of the RA

Cheyne-Stokes breathing is characterized by

a. periodic, cyclic clustering of RA
b. the onset of most periods which contain the RAs show the characteristics of central sleep apnea

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Sharpen YOur Calipers - Dr. Littmann

1/28/2016

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What is STEMI without STE?

Patients presenting with acute chest pain may have clinical STEMI (acute total thrombotic occlusion of a large coronary artery) but no obvious ST-segment elevation in the ECG
This occurs with STEMI locations that are not well represented by conventional ECG leads
Such patients are at high for not receiving timely reperfusion therapy and for having poor outcomes
Easily memorizable ECG signs can help raise awareness of the possibility of STEMI without STE
If suspected, placing exploring electrodes to the area of interest can quickly uncover the STEMI

Posterolateral or High Posterior MI

The most common type of missed STEMI
Almost always due to acute occlusion of the LCX
May involve the posterior papillary muscle and can cause severe mitral regurgitation
Earliest ECG sign: ST depression in the anterior chest leads (mirror image of posterior ST elevation)
Frequent associated findings: subtle Q waves or subtle ST elevation in the inferior or lateral leads
Can be uncovered by placing exploring electrodes to the back (V7-V8-V9)

High Lateral MI

The second most commonly missed STEMI
Almost always due to acute occlusion of the first diagonal branch of the LAD (LAD-D1)
Fortunately usually small
Earliest ECG sign: ST elevation in leads I, aVL and V2, but not in V1 or V3, and ST depression in III and aVF
With the conventional 4x3 lead display format, the spacing of ST deviation resembles the shape of the South African flag (the “South African Flag Sign”)
Can be uncovered by placing the V4-V5-V6 ECG leads 1 and 2 interspaces higher

RV infarct

Almost always due to acute occlusion of the proximal RCA
Almost always associated with acute inferior STEMI
Recognition of RV infarct, therefore, is now less important because code STEM is usually called anyway for the inferior MI
Recognition can be important, however, if the ST elevation in the inferior leads is subtle or nondiagnostic
Clues to suspect RV MI:
1. Inferior STEMI with marked ST depression in I and aVL (left leads)
2. Inferior STEMI with ST elevation in V1 only but not in V2
Can be uncovered by placing right-sided chest leads
If inferior STEMI has been diagnosed, there is no need to waste time to record right-sided chest leads
Suspected RV MI:
1. Use caution with vasodilators (nitrates)
2. Consider IV fluids for hypotension with JVD

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Runs of Wide-Complex Tachycardia on Telemetry - Dr. Littmann

11/12/2015

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Differential Diagnosis

SVT with aberrancy (SVT with RBBB or SVT with LBBB)
Nonsustained VT
Artifact
Uncertain (“I don’t know”) – this is a better choice than incorrect guessing!

When the intrinsic rhythm is sinus:
I. What was the first beat of the tachycardia?

If the first early beat was a PAC (premature P wave in front of the QRS) -> SVT
If the first early beat was a PVC (no premature P wave in front of the QRS) -> VT

II. What is the P-QRS relationship?

A-V dissociation present -> VT
More QRS complexes than P waves -> VT

III. Fusion complexes present? -> VT

Combination QRS morphology (QRS wider than during sinus but narrower than the widest QRS)
P waves must be present in front of the combination morphology QRS complexes

When the intrinsic rhythm is atrial fibrillation:

If the WCT is regular -> VT

Artifact
Always consider artifact if:

It is uncertain which was the first or the last beat of the WCT
The rate of the tachycardia was excessive
The patient remained asymptomatic during a long run of a very fast tachycardia

Prove artifact by demonstrating that the

Intrinsic QRS complexes march through
“Notches” march through
Simultaneous hemodynamic tracing indicates regularity

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Sharpen Your Calipers: Wide Complex Tachycardia - Dr. Littmann

9/10/2015

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General
1.     WCT algorithms do not work in the real life setting
2.     Don’t pay attention to what others have said; you need to evaluate the ECG yourself
3.     First question: is the WCT regular or irregular?

Sustained Regular WCT
I. Differential Diagnosis
1.     Sustained regular WCT: most likely ventricular tachycardia (VT)
a.     Spend 2 minutes searching for P waves – inconsistent P-QRS relationship is 100% specific for VT
b.     Bizarre QRS morphology that is not c/w RBBB or LBBB (negative QRS in lead I; QRS concordance in the chest leads) strongly supports VT

2.     Consider SVT if QRS morphology resembles RBBB or LBBB
a.     Find an old ECG: are the QRS morphologies identical?
b.     If no old ECG available, prove SVT by giving IV adenosine
c.     “I think this is SVT” is not good enough!

II. Therapy of Sustained Ventricular Tachycardia
1.     Unstable: electric cardioversion

2.     Clinically stable: one round of IV antiarrhythmic drug therapy allowed
a.     IV procainamide may be the most effective agent (avoid in patients with severe systolic CHF and
in patients with baseline prolonged QT)
b.     IV amiodarone
c.     Consider IV propranolol or IV metoprolol in ischemic VT and in patients with “electric storm”
(repeat episodes of VT/VF)

Sustained Irregular WCT

I. Differential Diagnosis
1.     Sustained irregular WCT: most likely not VT but atrial fibrillation (AF)
2.     Rate 120-160; QRS morphology is c/w RBBB or LBBB: AF with bundle branch block
3.     Rate very fast; QRS morphology is bizarre, not c/w RBBB or LBBB: most likely AF with WPW (FBI – Fast, Broad-complex, Irregular)

II. Therapy
1.     AF with BBB: usual therapy for AF (IV diltiazem etc.)
2.     AF with WPW (“FBI”)
a.     Clinically unstable or ventricular rate excessive: electric cardioversion
b.     Clinically stable: IV procainamide or IV ibutilide
c.     Clinically very stable, rate not very fast: PO flecainide or propafenone
NOT ALLOWED: IV verapamil, diltiazem, digoxin, adenosine

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Sharpen Your Calipers - Dr. Littmann

8/20/2015

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Bifascicular Block and Second Degree AV Block

1.     In asymptomatic individuals, chronic bifascicular block does not usually require cardiac work-up; the prognosis is generally benign

2.     The following high-risk features, however, warrant urgent evaluation:
a.   Bifascicular block and syncope
b.   Bifascicular block and intermittent second degree AV block
c.   1:1 AV conduction at slower sinus rates but higher grade block (i.e., 2:1 AV conduction) at faster
sinus rates (“acceleration-dependent AV block”)

3.     Evaluation and management of patients with bifascicular block:
a.   Actively search for nonconducted P waves in the 12-lead ECG
b.   Always review telemetry strips and actively search for episodes of second degree AV block
(blocked P waves)
c.   In symptomatic patients with bifascicular block who develop acceleration-dependent second
degree AV block and a very slow ventricular rate, carotid massage or IV beta blocker can
paradoxically restore 1:1 AV conduction
d.   Patients with bifascicular block and syncope require admission and cardiology consultation for
possible pacemaker implantation
e.   Patients with bifascicular block and intermittent second degree AV block require cardiology
consultation for possible pacemaker implantation

The Pacemaker ECG

1.     Ventricular pacing: always try to determine what the atria are doing

2.     Sinus P wave in front of each paced QRS complex indicates dual chamber (A-V sequential) pacemaker where the ventricular pacer is tracking sinus rhythm

3.     Two pacer spikes about 5 mm apart indicate AV sequential pacing

4.     If there are no P waves or 2 pacer spikes, search for the presence of retrograde P waves after the paced QRS complexes; retrograde P waves are sharp negative in the inferior leads (in II, III and aVF) and usually upright in V1

5.     If there are no P waves in front of the paced QRS complexes and no retrograde P waves present, always consider the possibility of underlying atrial fibrillation

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The significance of Respiratory artifact (RA) in the ECG - Dr. Littmann

Sharpen YOur Calipers - Dr. Littmann

Runs of Wide-Complex Tachycardia on Telemetry - Dr. Littmann

Sharpen Your Calipers: Wide Complex Tachycardia - Dr. Littmann

Sharpen Your Calipers - Dr. Littmann

Bifascicular Block and Second Degree AV Block

The Pacemaker ECG

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