Utility of Holter Electrocardiogram Monitoring in Iron over Loaded β Thalassemia and Sickle Cell Disease.
Authors: Qureshi Naveen , Avasarala Kishor , Singer Sylvia Titi , Foote Drucilla , Hackney-Stephens Ekua , Hagar Robert , Vichinsky Elliott P. 
Published: October 2019

Abstract
BACKGROUND: Cardiac disease is a leading cause of morbidity and mortality of β thalassemia and sickle cell (SCD) patients. Arrhythmias often precede the development of cardiomyopathy and can result in sudden death. Since early intervention may improve outcome, routine screening of iron overloaded patients with 24 hour Holter electrocardiographic analysis is recommended, although its usefulness has not been studied. Infrequent and unpredictable electrocardiographic changes in these patients may limit its usefulness.
The objective of this study is to determine the diagnostic yield of 24 hour holter EKG monitoring and its correlation with patient symptoms and disease status.
METHODS: 44 iron overloaded hemoglobinopathy patients underwent a cardiac questionnaire, standard 24 hour Holter monitoring, echocardiogram, quantitative liver iron by SQUID (Superconducting Quantum Interfering Device). A chart review was completed initially and repeated on follow up visits. Holter monitoring outcomes were classified into 3 groups: clinically significant, clinically insignificant and normal. Echocardiograms were classified as normal, normal with pulmonary hypertension and abnormal. Thalassemia and SCD were analyzed separately.
RESULTS: 27 transfusion dependent thalassemia patients at a mean age of 19 years (3–46), including 14 males and 13 females. Mean quantitative liver iron for the group was 15.0 mg/gm d/wt (3.3–46.4). 17 SCD patients had a mean age of 16.4 years, (11–33), including 9 males and 8 females. Mean quantitative liver iron for SCD was 13.5 mg/gm d/wt (3.3–46.4) and was similar to thalassemia. The questionnaire revealed cardiac symptoms, (palpitations, syncopy, etc.) were reported in 11/27 (40.7%) thalassemia patients, and in 1/17 (5.9%) sickle cell patient. In thalassemia, 4/27 (15%) of patients had clinically significant arrhythmias detected on holter (frequent PVCs, ventricular bigeminy, supraventricular tachycardia [SVT] and atrial flutter). Of the remaining, 37% of thalassemia patients had clinically insignificant holter findings and 48 % were normal. Age, sex, liver iron were similar in each holter subgroup. 30% of thalassemia patients had pulmonary hypertension (tricuspid regurgitant jet >2.5 ms) with normal echocardiogram. In addition, 50% of the clinically significant holter group demonstrated pulmonary hypertension. In SCD, there were no patients in the clinically significant holter group, 8/17 in the clinically insignificant group and 9 with normal findings. 29% (5/17) had pulmonary hypertension with normal echocardiograms.
On follow up, 3 patients (2 thalassemia and 1 SCD) developed acute cardiac complications secondary to arrhythmias. The first patient experienced frequent PVCs during the screening and 1 month later developed acute palpitations and dizziness associated with atrial flutter. The second patient, following a clinically insignificant screening developed months later, supraventricular tachycardia and atrial flutter. There were no predictive risk factors in these 3 patients. CONCLUSION: 14% of transfusion dependent thalassemia and SCD patients developed an abnormal EKG on screening or follow up. 3 patients experienced serious complications. Echocardiogram, pulmonary hypertension and iron stores were not predictive. Early detection of cardiac arrhythmias is indicated; however, the standard holter EKG method is insensitive. The transelephonic event recorder may be evaluated in arrhythmia surveillance in thalassemia.