Palpitation electrocardiogram

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Akash Daswaney, M.B.B.S[2]

Overview

A 12 lead ECG is an important diagnostic tool used in the initial evaluation of patients presenting with palpitations. Based on the presence or absence of positive ECG findings physicians can determine the need for ambulatory ECG monitoring, echocardiograpy, lab investigations or electrophysiology study.

Electrocardiogram

• A 12 lead ECG along with a detailed history and thorough physical examination form the cornerstone trio in initially approaching a patient presenting with palpitations.
• It should be noted that a patient is rarely symptomatic at the time of presentation as palpitations are frequently a transitory symptom.
• However, this should not take away from an ECG’s importance as an initial diagnostic procedure.
• Nicolas Clementy et al at found that prehospital ECGs and ECGs at admission had the highest positivity rate.
• Based on the presence or absence of ECG findings, a decision should then be made whether the underlying condition is cardiac or not and what further investigative modalities may be required.

• Several studies have suggested that an aggressive diagnostic approach should be employed in patients who are :
  1. At a high risk of developing arrhythmias (presence of ECG changes on initial evaluation, H/O myocardial and structural heart disease, positive family history)
  2. Those who remain anxious to have a specific explanation regarding their symptoms.
  3. Patients with a history of warning symptoms such as presyncope, syncope, dizziness, dyspnea.
  4. Patients with a history of increase of palpitations on exertion.
  5. Patients with impaired hemodynamic function.
  6. Patients with an impaired quality of life attributable to palpitations.

Findings to be wary of on initial 12 Lead ECG Evalutation

	Epidemiology	Rate	Rhythm	P waves	PR Interval	QRS complex	Response to maneuvers	Example (Lead 2)
Sinus Tachycardia	More common in children and elderly.	Greater than 100 bpm	Regular	Upright, consistent, and normal in morphology	0.12–0.20 sec and shortens with high heart rate	Less than 0.12 seconds, consistent, and normal in morphology	May break with vagal maneuvers
Atrial Fibrillation	More common in the elderly, following bypass surgery, in mitral valve disease, hyperthyroidism	110 to 180 bpm	Irregularly irregular	Absent, fibrillatory waves	Absent	Less than 0.12 seconds, consistent, and normal in morphology in the absence of aberrant conduction	Does not break with adenosine or vagal maneuvers
Atrial Flutter	More common in the elderly, after alcohol	75 (4:1 block), 100 (3:1 block) and 150 (2:1 block) bpm, but 150 is more common	Regular	Sawtooth pattern of P waves at 250 to 350 beats per minute	Varies depending upon the magnitude of the block, but is short	Less than 0.12 seconds, consistent, and normal in morphology	Conduction may vary in response to drugs and maneuvers dropping the rate from 150 to 100 or to 75 bpm
AV Nodal Reentry Tachycardia (AVNRT)	Accounts for 60%-70% of all SVTs. 80% to 90% of cases are due to antegrade conduction down a slow pathway and retrograde up a fast pathway.	In adults the range is 140-250 bpm, but in children the rate can exceed 250 bpm	Regular	The P wave is usually superimposed on or buried within the QRS complex	Cannot be calculated as the P wave is generally obscured by the QRS complex	Less than 0.12 seconds, consistent, and normal in morphology	May break with adenosine or vagal maneuvers
AV Reciprocating Tachycardia (AVRT)	More common in males, whereas AVNRT is more common in females, occurs at a younger age.	More rapid than AVNRT	Regular	A retrograde P wave is seen either at the end of the QRS complex or at the beginning of the ST segment	Less than 0.12 seconds	Less than 0.12 seconds, consistent, and normal in morphology	May break with adenosine or vagal maneuvers
Inappropriate Sinus Tachycardia	The disorder is uncommon. Most patients are in their late 20s to early 30s. More common in women.	> 95 beats per minute. A nocturnal reduction in heart rate is present. There is an inappropriate heart rate response on exertion.	Regular	Normal morphology and precede the QRS complex	Normal and < 0.20 seconds	Less than 0.12 seconds, consistent, and normal in morphology	Does not break with adenosine or vagal maneuvers
Junctional Tachycardia	Common after heart surgery, digitalis toxicity, as an escape rhythm in AV block	> 60 beats per minute	Regular	Usually inverted, may be burried in the QRS complex	The P wave is usually buried in the QRS complex	Less than 0.12 seconds, consistent, and normal in morphology	Does not break with adenosine or vagal maneuvers
Multifocal Atrial Tachycardia (MAT)	High incidence in the elderly and in those with COPD	Atrial rate is > 100 beats per minute (bpm)	Irregular	P waves of varying morphology from at least three different foci	Variable PR intervals, RR intervals, and PP intervals	Less than 0.12 seconds, consistent, and normal in morphology	Does not terminate with adenosine or vagal maneuvers
Sinus Node Reentry Tachycardia	Between 2% and 17% among individuals undergoing EKG for SVTs	100 to 150 bpm	Regular	Upright P waves precede each regular, narrow QRS complex	Short PR interval	Less than 0.12 seconds, consistent, and normal in morphology	Does often terminate with vagal maneuvers unlike sinus tachycardia.
Wolff-Parkinson-White syndrome	Estimated prevalence of WPW syndrome is 100 - 300 per 100,000 in the entire world.	Atrial rate is nearly 300 bpm and ventricular rate is at 150 bpm.	Regular	P wave generally follows the QRS complex due to a bypass tract	Less than 0.12 seconds	Delta wave and evidence of ventricular pre-excitation if there is conduction to the ventricle via ante-grade conduction down an accessory pathway	May break in response to procainamide, adenosine, vagal maneuvers

Disease	ECG Findings	Example
Left Ventricular Hypertrophy	Increased R wave amplitude in the left-sided ECG leads (I, aVL and V4-6) and increased S wave depth in the right-sided leads (III, aVR, V1-3).
Extrasystolic Palpitations/Ventricular Tachycardia	Frequent Premature ventricular contractions.
Ischemic Heart Disease	Q waves, T wave inversions, ST segment elevations or depressions.
Hypertrophic Cardiomyopathy	Tall R waves in aVL, deep S waves in V3 and T waves changes.
Arrhythmogenic right ventricular cardiomyopathy	Inverted T waves or Epsilon waves across right precordial leads (V1-V3)
Long QT syndrome	QT interval longer than 460 msec in women and 440 msec for men.
Genetic Arrhythmia syndromes	Long or Short QT interval, Brugada pattern, early repolarisation pattern.

Ambulatory Electrocardiography

• Ambulatory ECG devices can be divided into internal and external monitoring devices.
• External Devices include Holter monitors, hospital telemetry devices, event recorders, external loop recorders and mobile cardiac outpatient telemetry.
• Internal devices include pacemakers, implantable cardioverter defibrillators equipped with diagnostic features and implantable loop recorders.
• In addition, modifications to monitoring devices have permitted automatic detection of arrythmia.
• Data is wirelessly transmitted to a central monitoring station which then triggers off an alarm in case of an event.
• This allows for prompt responses from the physician, facilitates early detection of episodes and provides information regarding the mechanism of the arrythmia.
• It is important to note that while the specificity of ambulatory ECG monitoring is high in terms of differentiating between arrhythmogenic and non-arrhythmogenic causes of palpitations, it’s sensitivity depends on the duration of monitoring, patient compliance and the frequency of episodes.

ACC/AHA Guidelines for Ambulatory Electrocardiography

Indications for Ambulatory Electrocardiography

Different Ambulatory Electrocardiography Devices

Machine	Description	Indications	Advantages	Disadvantages	Picture
12 Lead ECG		•Initial Step in the evaluation of patients of palpitations	•Inexpensive	•Rarely performed during the event
Handheld ECG		•Palpitations occurring for months to years	•High diagnostic yield •Always present with the patient	•Expensive •Time period from patient activation to event recording is long
Exercise ECG Stress testing		•Palpitations aggravated by exertion
Holter Monitoring	•Continuous beat to beat monitoring system via 12 leads (attached via skin electrodes). •24-48 hour monitoring system.	•Symptoms occurring daily or every second day.	•Readily available. •Need not be activated during the event. •Low cost. •Provides information of asymptomatic episodes.	•Low diagnostic yield •Size may prevent trigger events •Clinical Diary completion (upon which symptom correlation depends upon) is a tedious process	A person carries a holter monitor in his pocket.
Continuous- loop event recorder	•Worn for a few days (typically 30 days) •Older monitors are patient activated and store data once, whereas newer models continuously record data •Provides a one to three lead EKG tracing	•Symptoms occurring weekly or monthly •Short lasting palpitations associated with hemodynamic compromise	•Can be worn for longer periods of time when compared to Holter monitors •More cost effective •High diagnostic efficacy/yield as it is a patient activated process	•Not diagnostic for asymptomatic arrythmias as it is a patient activated system (older models •Devices are uncomfortable and require high maintenance •Requires patient to be compliant
Mobile cardiac outpatient telemetry	•External Loop Recorder + Portable Receiver •Data is wirelessly transmitted to a central monitoring station which then triggers off an alarm in case of an event		•This allows for prompt responses from the physician, facilitates early detection of episodes and provides information regarding the mechanism of the arrythmia •Provides information of asymptomatic episodes.
Implantable Loop Recorder	•Placed subcutaneously through a small 2cm incision in the left precordial region •Provides a one lead electrocardiographic tracing	•Palpitations occurring for months to years •Rare episodes of palpitations associated with syncope/ hemodynamic compromise •When all other methods of Ambulatory ECG monitoring prove to be inconclusive	•High diagnostic yield • Long term monitoring (3 years) •Automatically records arrythmias in addition to patient triggered episodes •Subcutaneous approach avoids long term problems associated with surface electrodes •Does not require patient to be compliant.	•Invasive procedure may cause local complications •Expensive •Not readily available
Pacemakers/Implantable Cardioverter Defibrillators	•Dual chamber Devices which are able to detect and store atrial and ventricular Intracardiac Electrograms.	•Conventional indications for pacemakers/ICDs	•Automatic Arrythmia recording •Able to discriminate between ventricular and supraventricular arrythmias	•Invasive •Increased risk of early/long term local/systemic complications	Pacemaker insitu.

• Allan Abbott et al found that transtelephonic event monitors had a greater diagnostic yield and were more cost effective when compared to Holter monitors.