'Inappropriate' Sinus Tachycardia
Sinus tachycardia is commonly encountered in clinical practice and when persistent, can result in significant symptoms and impaired quality of life, warranting further evaluation. On the other hand, a growing body of epidemiological and clinical evidence has shown that high resting heart rate (HR) within the accepted normal range is independently associated with increased risk of all-cause and cardiovascular mortality. However, higher HR as a risk factor for adverse cardiovascular outcomes is frequently underappreciated. In this review, we focus on two challenging problems that span the spectrum of abnormally fast sinus HR. The first section reviews inappropriate sinus tachycardia, a complex disorder characterized by rapid sinus HR without a clear underlying cause, with particular emphasis on current management options. The latter section discusses the prognostic significance of elevated resting HR and reviews clinical evidence aimed at modifying this simple, yet highly important risk factor.
Heart rate (HR) is perhaps the most frequently monitored vital sign and affects medical decision-making in everyday clinical practice. It is a key determinant of myocardial work and metabolic requirements. Of the cardiac arrhythmias, sinus tachycardia (ST; sinus rate >100 bpm) is perhaps the most frequently encountered in clinical practice. The evaluation and management of ST involves careful assessment to determine whether tachycardia is an appropriate response to an underlying illness. This appropriate ST can be secondary to a variety of pathological conditions whose discussion is beyond the scope of this article.
However, a small proportion of patients, mostly young adults, have marked resting ST without underlying secondary causes or structural heart disease. This can often lead to debilitating symptoms and is referred to as inappropriate ST (IST). IST is an often under-recognized problem with significant morbidity. There is a paucity of knowledge with regards to the pathophysiology of IST and this, along with identifying effective management options, remains an active area of research.
Animal studies first noted that increased HR is associated with detrimental vascular effects and decreased survival. Epidemiological, as well as human, clinical trials have provided further evidence for a strong association between elevated HR and adverse cardiovascular outcomes. Over the course of the past few years, high resting sinus HR within the normal range of 60–100 bpm has become an exciting area of investigation as more and more data have emerged supporting its role in predicting hard clinical end points, and has led to suggestions that it is time to redefine tachycardia. This has resulted in the trial of pharmacological approaches at ameliorating this risk.
In this review, we focus on the pathophysiology, clinical characteristics, diagnosis and management of IST. We also review the prognostic significance of high resting sinus HR, as well as outcome data on the ability to modify this important clinical variable.
Abstract and Introduction
Abstract
Sinus tachycardia is commonly encountered in clinical practice and when persistent, can result in significant symptoms and impaired quality of life, warranting further evaluation. On the other hand, a growing body of epidemiological and clinical evidence has shown that high resting heart rate (HR) within the accepted normal range is independently associated with increased risk of all-cause and cardiovascular mortality. However, higher HR as a risk factor for adverse cardiovascular outcomes is frequently underappreciated. In this review, we focus on two challenging problems that span the spectrum of abnormally fast sinus HR. The first section reviews inappropriate sinus tachycardia, a complex disorder characterized by rapid sinus HR without a clear underlying cause, with particular emphasis on current management options. The latter section discusses the prognostic significance of elevated resting HR and reviews clinical evidence aimed at modifying this simple, yet highly important risk factor.
Introduction
Heart rate (HR) is perhaps the most frequently monitored vital sign and affects medical decision-making in everyday clinical practice. It is a key determinant of myocardial work and metabolic requirements. Of the cardiac arrhythmias, sinus tachycardia (ST; sinus rate >100 bpm) is perhaps the most frequently encountered in clinical practice. The evaluation and management of ST involves careful assessment to determine whether tachycardia is an appropriate response to an underlying illness. This appropriate ST can be secondary to a variety of pathological conditions whose discussion is beyond the scope of this article.
However, a small proportion of patients, mostly young adults, have marked resting ST without underlying secondary causes or structural heart disease. This can often lead to debilitating symptoms and is referred to as inappropriate ST (IST). IST is an often under-recognized problem with significant morbidity. There is a paucity of knowledge with regards to the pathophysiology of IST and this, along with identifying effective management options, remains an active area of research.
Animal studies first noted that increased HR is associated with detrimental vascular effects and decreased survival. Epidemiological, as well as human, clinical trials have provided further evidence for a strong association between elevated HR and adverse cardiovascular outcomes. Over the course of the past few years, high resting sinus HR within the normal range of 60–100 bpm has become an exciting area of investigation as more and more data have emerged supporting its role in predicting hard clinical end points, and has led to suggestions that it is time to redefine tachycardia. This has resulted in the trial of pharmacological approaches at ameliorating this risk.
In this review, we focus on the pathophysiology, clinical characteristics, diagnosis and management of IST. We also review the prognostic significance of high resting sinus HR, as well as outcome data on the ability to modify this important clinical variable.
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