To the Editor - Maternal inappropriate sinus tachycardia during pregnancy.

Abstract

Shah and colleagues presented 11 patients with maternal inappropriate sinus tachycardia (IST) during pregnancy.1Shah AN, Ferreira SW, Padanilam BJ, Prystowsky EN. Management of inappropriate sinus tachycardia during pregnancy. Heart Rhythm O2. 2022. DOI: http://doi.org/10.1016/j.hroo.2022.11.001Google Scholar Two major points are worth considering. First, the authors used a definition for IST consistent with the 2015 Heart Rhythm Society expert consensus statement.1Shah AN, Ferreira SW, Padanilam BJ, Prystowsky EN. Management of inappropriate sinus tachycardia during pregnancy. Heart Rhythm O2. 2022. DOI: http://doi.org/10.1016/j.hroo.2022.11.001Google Scholar,2Sheldon RS. Grubb BP 2nd, Olshansky B, et al. 2015 Heart Rhythm Society expert consensus statement on the diagnosis and treatment of postural orthostatic tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope. Heart Rhythm. 2015;12:e41-e63.Google Scholar This included a resting heart rate >100 beats/min and an average heart rate >90 beats/min on 24-hour monitoring. Yet, heart rate criteria were derived from non-pregnant individuals. In healthy pregnancy, heart rates >100 beats/min have been observed in more than 10% of subjects from 18 weeks of gestation.3Green L.J. Mackillop L.H. Salvi D. et al.Gestation-specific vital sign reference ranges in pregnancy.Obstet Gynecol. 2020; 135: 653-664Crossref PubMed Scopus (42) Google Scholar Some have suggested that a threshold of 100 beats/min is too low for the upper limit of normal in pregnancy.4Coad F. Frise C. Tachycardia in pregnancy: when to worry?.Clin Med. 2021; 21: e434-e437Crossref PubMed Scopus (3) Google Scholar Maternal IST during pregnancy requires a modification to the present definition. Maintaining the present diagnostic criteria will likely result in overdiagnosis. Second, effectiveness and safety of metoprolol succinate remains questionable. Lifestyle modifications, such as increased fluid intake for volume expansion, is often recommended in IST.2Sheldon RS. Grubb BP 2nd, Olshansky B, et al. 2015 Heart Rhythm Society expert consensus statement on the diagnosis and treatment of postural orthostatic tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope. Heart Rhythm. 2015;12:e41-e63.Google Scholar These alone may improve symptoms. Generally, the performance of β-blockers for IST in non-pregnant patients is considered underwhelming.5Olshansky B. Sullivan R.M. Inappropriate sinus tachycardia.Europace. 2019; 21: 194-207Crossref PubMed Scopus (32) Google Scholar,6Ahmed A. Pothineni N.V.K. Charate R. et al.Inappropriate sinus tachycardia: etiology, pathophysiology, and management.J Am Coll Cardiol. 2022; 79: 2450-2462Crossref PubMed Scopus (0) Google Scholar Moreover, although metoprolol is considered to be one of the safer β-blockers for use during pregnancy, one study reported low birth weight (<2500 grams) in 13.3% of infants with intrauterine exposure to metoprolol compared to 5.2% in non-exposed controls.7Duan L. Ng A. Chen W. Spencer H.T. Lee M.S. Beta-blocker subtypes and risk of low birth weight in newborns.J Clin Hyperten. 2018; 20: 1603-1609Crossref Scopus (32) Google Scholar There should be caution when considering dose escalation of metoprolol succinate. As cardiac electrophysiologists become involved in developing cardio-obstetric teams, it is prudent to be aware that many diagnosis and treatment patterns for non-pregnant patients may need to be adjusted for pregnant patients. Authors’ Reply to the Editor—Maternal inappropriate sinus tachycardia during pregnancyHeart Rhythm O2PreviewWe would like to comment on the Letter to the Editor of Dr Wang on our manuscript, Management of Inappropriate Sinus Tachycardia during pregnancy (1). Full-Text PDF Open Access