Image of the Day 11: The Missing Heartbeat

This is a plain radiograph of a 20 years old female who presented with palpitation. On examination, the pulse is tachycardic and irregularly irregular. On chest examination, there was no apex beat palpable and on auscultation, no heart sound heard.

Well, the chest radiograph will give you an easy answer that this is a dextrocardia. But, when you examine a patient with unknown history of dextrocardia or pre existing plain radiograph, the diagnosis of dextrocardia should be on the last of the list. The most common reason of why you can not feel the heartbeat is the obesity or thick chest wall. Other reason would be tension pneumothorax, massive pleural effusion, cardiac temponade, COPD patient and condition associated with poor ventricular filling like shock. And of course, if patient is already dead then there will be no heart beat. But dead person will not talk or staring at you right! So in exam, dont ever answer this as a differential diagnosis if you are examining alive patient.

Dextrocardia is the anomaly of the heart position in which it is located at the right hemithorax. The base to apex axis is directed to the right and caudad. It is purely due to the anomaly of the heart and not by the extra cardiac abnormalities. Meanwhile, Levocardia is the normal position of the apex of the heart like all we have.

The extra cardiac abnormalities like right lung hypoplasia, right pneumonectomy and diaphragmatic hernia will also cause the heart to be on the right hemithorax in which this condition is termed as cardiac dextroposition. Hence give you more differentials for the absent heartbeat.

Now that you know about the causes of missing heartbeat, brief intro on dextrocardia and cardiac dextroposition, therefore let us revise on the most confusing part which is the relation of the heart and other organ or simply known as situs.

To be exact, situs actually means the configuration of asymmetric structures within an individuals. It is further divided into three namely 1) Solitus (normal), 2) Inversus(mirror image) and 3) ambiguous (the most rare and bizzare anomalies in which there is mixed of solitus and inversus, missing of organ or duplication of organ). It is also known as heterotaxy.

The apex of the heart will be correspondence with other viscera situs. Therefore, if the heart is the only organ that is in dextrocardia position, therefore it is a situs solitus dextrocardia. It means that the apex of the heart which is supposed to be on the left sided of the body is in the right side.Otherwise, other organ has it's normal axis. To make you understand this; The right lung still have three lobe and left lung have two lobe and the apex is facing the three lobes's right lung.

If the whole organ is in mirror image, it is named as situs inversus totalis. It means that the apex of the heart is on the same site of the viscera mirror image. For example, the apex is sitting on the right thorax in which the right lung has two lobe and the left lung has three lobe.

In third type, there may be added abnormalities like the internal organ in inversus and may be associated with duplicated organ, missing organ or abnormally form organ. For example, in asplenia syndrome or Ivemark's syndrome , the spleen is absent and right-sided structures are duplicated, with bilateral trilobed lungs containing eparterial bronchi. Both atria resemble morphologic right atria. The liver is symmetric and horizontal, and the stomach tends to be near the midline. [Pierre D.M & Muhamed S]. Polysplenia syndrome is characterized by multiple small spleens, usually adjacent to the stomach, with duplication of left-sided structures, especially bilateral bilobed lungs with hyparterial bronchi. Both atria may resemble morphologic left atria. The tendency to symmetry of the abdominal organs is not as pronounced as in asplenia [Pierre D.M & Muhamed S].

For more understanding on what i’m talking about, you may read the reference to this article. The differential of the missing heartbeat is IMPORTANT but the rest is NOT SO. It is just a sharing purpose and will not even come in exam.

Reference

1)         Annamaria Wilhelm, "Situs Inversus Imaging", 

http://emedicine.medscape.com/article/413679-overview   

2)         Kent Ellis, Richard J. Fleming et al, "New Concepts in Dextrocardia", AJR June 1966 vol. 97 no. 2 295-313

3)         Pierre D. Maldjian & Muhamed Saric, "Approach to Dextrocardia in Adults: Review", AJR:188, June 2007

4)         A Bernasconi, A Azancot et al, "Fetal dextrocardia: diagnosis and outcome in two tertiary centres", Heart 2005;91:1590–1594.