Definition

  Dextrocardia: Electrical axis of the heart is directed inferiorly and to the right. There are several variants of dextrocardia:

      1.
Dextrocardia and situs inversus (mirror image dextrocardia): in addition to the heart, internal organs

          of abdomen are also positioned on the opposite side.

      2.
Dextrocardia and situs solitus: Only heart is on the opposite side; internal organs are not affected.

 
Dextroposition: The anatomically corrected heart is displaced to the right hemithorax.

      Causes: deformities of chest wall, deformities of diaphragm, postpneumonectomy, hypoplastic right lung,

      eventration of diaphragm, left hemidiaphragmatic paralysis, pneumomediastinum.

 
Mesocardia: The heart is placed in the midline of thorax.

      Apex of the heart is either in the midline or directed towards right.

 
Heterotaxy: (abnormal placement) Thoracic and abdominal organs are are placed abnormally.

      There is no right-left relationship between the organs: neither situs solitus, nor situs inversus.




ECG criteria

  In mirror-image dextrocardia, the axes of P, QRS and T waves are directed to the right and inferior.

  This results in positive P waves in leads III and aVF and negative P waves in leads I and aVL.

      Not only the P wave, but QRS complex and T waves are also negative in lead I.

  In dextrocardia, normal progression of the R wave
is not observed in chest leads.



Differential diagnosis

  When arm leads are reversed the P waves become negative in lead I and positive in lead aVR.

      In addition to the P wave, QRS complex and T wave are also negative in lead I.

  However,
reversal of arm leads does not affect R progression in chest leads

      and results in an increase in R wave amplitude from lead C1 to C5:
normal R wave progression.



Clinical significance

  In a patient with dextrocardia, it will be easier to comment on the ECG

      if the chest electrodes are symmetrically placed on right chest and the arm leads are reversed.




Reference

  Military Medicine 2007;172:vii-ix.





Figure 1. Dextroposition, mirror-image dextrocardia and congenitally corrected transposition of the great arteries.

The above figure is a modified version of a figure that originally appeared in Military Medicine 2007;172:vii-ix (
with permission).






ECG 1a. The ECG above belongs to a 30 years-old woman. Precordial electrodes are placed on left chest (standard placement).
There is no R progression in chest leads. Calibration is at 10 mm/mV.

Click here for a more detailed ECG




ECG 1b. In order to see the P waves of limb leads more clearly, the ECG was recorded again at a calibration of 20mm/mV.
The chest electrodes are still on the left side. The P wave is negative in leads I and II, but positive in leads III and aVF.
No R wave progression is seen in the anterior leads.

Click here for a more detailed ECG




ECG 1c. The above ECG belongs to the same patient. This time, chest electrodes are symmetrically placed on right chest and
arm leads are reversed purposefully. Now, R wave progression is seen in anterior leads and the P wave is upright (positive)
in leads I and II. The ECG is calibrated at 10 mm/mV.

Click here for a more detailed ECG




ECG 1d. The electrodes are placed same as in ECG 1c; only the calibration is 20 mm/mV.

Click here for a more detailed ECG





ECG 2a. This ECG belongs to a 52 years old man who had undergone stenting of the right coronary artery for the treatment of
acute inferior wall myocardial infarction 1 year ago. The ECG above was recorded during a routine control and the patient
was asymptomatic. There are
Q waves and negative T waves in the inferior leads. Lacking ST elevation and typical chest pain,
these ECG findings suggest OLD inferior wall myocardial infarction. The patient also has dextrocardia. Because of
dextrocardia,
QRS complex and T wave are upright in lead aVR while they are negative in lead I . This finding is not due to
arm lead reversal since there is no expected R wave progression in the chest leads. Contrarily, the
amplitude of the R wave
decreases from C1 to C6.

Click here for a more detailed ECG




ECG 2b. The above ECG belongs to the same patient but was recorded after the electrodes were symmetrically placed on the
right chest. The ECG now shows proper
R wave progression . Old inferior myocardial infarction and abnormal appearance in
lead aVR persists.

Click here for a more detailed ECG





ECG 3a. The ECG tracing above belongs to an 11 years-old girl and shows leads I, II and III. She has right lung agenesis
(complete absence of right lung) and dextrocardia.
You can see her thorax MR images at: International Journal of Cardiology 2011 Nov 14: doi:10.1016/j.ijcard.2011.10.069

Dr. Andrea Barison has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 3b. Leads aVR, aVL and aVF of her ECG.

Dr. Andrea Barison has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 3c. Leads V1, V2 and V3 of her ECG.

Dr. Andrea Barison has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 3d. Leads V4, V5 and V6 of her ECG.

Dr. Andrea Barison has donated the above ECG to our website.

Click here for a more detailed ECG






ECG 4a. The ECG above is from a 41 years-old woman who had previously undergone VSD repair and hemodynamically stable
at the moment. It was recorded in the emergency department when she complained of intermittent palpitation.
P waves are negative in leads I, aVL and V1 to V6, while they are upright in lead aVR.
Right arm-left arm electrode misplacement may explain negative P waves in leads I and aVL but not those in precordial leads.
There seems to be right bundle branch block (RBBB) in the above ECG, at first glance.
However, wide S waves are expected in lateral leads in right bundle block (which is not the case in the above ECG).
The wide QRS complexes may then be explained by intraventricular conduction defect.
However better auscultation of heart sounds from the right hemithorax suggests
dextrocardia in this patient.
PR interval is also prolonged (1st degree AV block) in the above ECG.


Click here for a more detailed ECG

The ECG above have been used with the permission of Netherlands Heart Journal.

Click here to read the relevant article by John J. et al.




ECG 4b. With the diagnosis of dextrocardia, the chest electrodes were symmetrically placed on right hemithorax and the
limb lead electrodes were reversed. The new ECG now displays right bundle branch block and 1st degree AV block (above).
P waves are normalized. The wide S waves expected in lateral leads right during right bundle branch block are also seen.
This case illustrates that if dextrocardia is not recognized and electrodes are not placed accordingly, right bundle branch
block may be falsely diagnosed as intraventricular conduction defect.


Click here for a more detailed ECG

The ECG above have been used with the permission of Netherlands Heart Journal.

Click here to read the relevant article by John J. et al.