Abstract
Situs inversus totalis with dextrocardia is a rare congenital occurrence. Risk of coronary atherosclerosis and acute myocardial infarction in this subset is similar to that in the general population. Diagnosing myocardial injury in time, and executing primary percutaneous coronary intervention (PCI) successfully in these patients is challenging given that physicians are rarely attuned to recognizing the electrocardiographic changes of acute coronary syndromes in this anatomy and interventional cardiologists are not routinely accustomed to working with the angiographic projections in this unique subset. Here, we describe electrocardiogram identification and an approach to primary PCI in one such patient. We have also attempted to simplify and refine primary PCI in this subset by introducing postero-anterior projection single inversion technique for suitable lesions in suitable vessels in this unique subset.
< Learning objective: Angioplasty of a diseased left anterior descending artery (LAD) in situs inversus dextrocardia can be simplified by using the postero-anterior (PA) projection predominantly, [thus eliminating the need for the need for right anterior oblique/left anterior oblique swapping (the reverse technique)], and utilizing only right-left reversal by activating horizontal sweep reverse option while filming the proximal (caudal tilt) and distal LAD (cranial tilt) to reorient the vessel in a viewer friendly equivalent. This we called the PA projection-single inversion technique for LAD in situs inversus dextrocardia.>
Introduction
Situs inversus dextrocardia is a rare condition in which the heart is located in the right thoracic cavity with its apex pointing to the right with the other thoracic and abdominal viscerae in mirror image positions of their normal location. Estimated prevalence of situs inversus dextrocardia in the general population is about 1:8000 to 1:10,000. Risk of coronary atherosclerosis and acute myocardial infarction (MI) in this population is similar to that of the general population . There are few case reports of acute MI in dextrocardia but detailed descriptions of electrocardiogram (ECG) identification and approach to emergency primary percutaneous coronary intervention (PCI) are lacking. We describe a case of successful primary PCI in acute MI in a patient with situs inversus totalis dextrocardia.
Case report
A 33-year-old man with previously identified situs inversus totalis dextrocardia presented with severe retrosternal chest pain of 4 hours’ duration. He was a chronic smoker with >10 pack-years history. Physical examination revealed right-sided apex beat with normal heart sounds. A 12-lead ECG was taken placing the limb leads and chest leads in their usual positions ( Fig. 1 A). Since the ECG findings agreed with the possibility of mirror image dextrocardia and were suggestive of ST-segment elevation MI, a corrected ECG ( Fig. 1 B) was taken by reversing left and right limb leads, swapping the respective positions of chest leads V1 and V2 and placing leads V3–6 in their respective mirror image positions on the right side of the chest.
This confirmed the diagnosis of dextrocardia, atrial situs inversus, acute anterior wall ST-segment elevation myocardial infarction. The patient received loading dose of dual antiplatelets and was shifted to the catheterization laboratory for primary PCI. Through right femoral artery access using a 5 French (F) Judkin’s right catheter, coronary angiogram (CAG) of right coronary artery (RCA) was performed which revealed dominant RCA with thrombolysis in myocardial infarction grade (TIMI) III flow and no noteworthy obstruction. Using 6F Extra Back Up guiding catheter, left CAG was done which showed total occlusion of proximal left anterior descending (LAD) artery. Using a workhorse coronary guidewire, the lesion was crossed and two rounds of thrombus aspiration performed. Post thrombosuction angiogram revealed 70% residual stenosis in the proximal LAD. Door to balloon time was approximately 1 hour and 10 minutes. The lesion was stented with a 3.0 × 28 mm drug-eluting stent. Post dilatation was done with a 3.0 × 20 mm non-compliant balloon. The final angiogram revealed no residual stenosis with TIMI III flow in LAD. The patient was discharged in stable condition on the sixth post-procedure day.
Discussion
Treating acute MI in dextrocardia poses difficulty at several levels starting from timely recognition of clinical features (especially in previously unidentified cases) to the proper performance of emergency primary PCI. Chest pain is the most common symptom in acute MI but in dextrocardia, this can be right sided with or without radiation to right shoulder and arm .
ECG remains the primary diagnostic tool to identify acute MI in mirror image dextrocardia too, but a standard 12-lead ECG taken placing leads in the usual position in such a patient can be misleading. Getting a corrected ECG is very important in patients with this anatomy .
PCI for acute MI in this subset has evolved and has been refined by various operators over time. Earlier case reports showed that PCI could be done either through transfemoral , , , or transradial , approach using routinely used left and right coronary guiding catheters but applying a reverse torque in place of conventional torque to engage the coronaries. Interpreting angiographic views in patients with dextrocardia is difficult. Reversing the right anterior oblique (RAO) / left anterior oblique (LAO) projection using LAO projection in a situation where RAO projection is normally done (and vice versa) but retaining cranial/ caudal tilt in the original manner is the most commonly used technique which gives reverse views. Double inversion technique (the addition of right-left reversal using horizontal sweep reverse option on the fluoroscopy machine to the reverse technique) is extremely useful as it orients the vessels to a form that one is familiar with.
In our case, we performed PCI using transfemoral approach, using reverse torqueing of the catheter to engage the coronaries and utilized horizontal sweep reverse technique to film the angiograms. Since the anatomy in our patient permitted working with limited angulation, we performed the procedure primarily in postero-anterior (PA) projection and avoided LAO and RAO projections thereby eliminating the need to swap views. The procedure was thereby simplified negating the need to use reverse technique (i.e. LAO in place of RAO) as we employed only PA projection with either cranial and caudal tilt. Utilizing limited diluted contrast, images taken in PA projection with and without adding right-left reversal by horizontal sweep reverse option are shown for relative comparison ( Fig. 2 A-F).
