Pregnancy Related Inappropriate Sinus Tachycardia

Study Overview
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Brief Summary
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A feasibility study into the exploration of possible mechanisms underlying inappropriate sinus tachycardia (IST) syndrome in pregnancy.

Detailed Description
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This is a non-interventional, physiological study which will explore the feasibility of examining autonomic function and related haemodynamic variables in pregnant women with and without inappropriate sinus tachycardia, with the aim of providing scope for future research. Sinus tachycardia (normal heart rhythm but fast heart rate) is common and usually related to an obvious cause (e.g. exercise such a running or cycling) and doesn't cause any untoward symptoms. In rare cases however, sinus tachycardia can occur without an obvious cause (i.e. it is inappropriate to the situation) and can cause distressing symptoms such as palpitations, dizziness and breathlessness at rest or with minimal exertion. This syndrome of inappropriate sinus tachycardia is poorly understood and can be difficult to manage; especially when the affected individual is pregnant. In order to understand the condition better and improve care pathways we aim to measure various features of the cardiovascular system in pregnant women with and without IST.

Official Title
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Pregnancy Related Inappropriate Sinus Tachycardia Syndrome Study

Conditions
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Inappropriate Sinus Tachycardia, Pregnancy Related

Intervention / Treatment
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* Diagnostic Test: ECG
* Diagnostic Test: heart rate monitor
* Diagnostic Test: Autonomic Nervous System (ANS) Activity
* Diagnostic Test: Haemodynamic variables
* Other: Echocardiogram


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged 18-45 years of age Able to give written informed consent and willing to participate The participant falls into one of the below categories: i. Pregnant women with IST ii. Pregnant women without IST Exclusion Criteria: Obesity (BMI > 29.9) Current or recent (within last 3 months) smoker Known medical condition likely to affect HRV (other than IST in relevant groups) Previous history of hypertensive disorders in pregnancy Lack of written informed consent

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Pregnant Healthy<br>Pregnant females aged between 18-45 years who do not have IST syndrome | Diagnostic Test: ECG<br>* 12-lead electrocardiogram<br>Diagnostic Test: heart rate monitor<br>* 24-hour heart rate monitor used to calculate mean heart rate and heart rate variability<br>Diagnostic Test: Autonomic Nervous System (ANS) Activity<br>* Heart Rate Variability (HRV) and Baroreflex sensitivity (BRS): Resting and exercise HRV and BRS calculated from ECG, Dundee Step test and blood pressure measurements.<br>Diagnostic Test: Haemodynamic variables<br>* Cardiac output (CO), stroke volume (SV) and systematic vascular resistance (SVR) will be assessed and calculated using a non-invasive, inert gas re-breathing technique whereby expired gases will be sampled and analysed alongside and blood pressure measurements.<br>Other: Echocardiogram<br>* optional (for non-IST participants only)<br>|
| Pregnant IST<br>Pregnant females aged between 18-45 years who have IST syndrome | Diagnostic Test: ECG<br>* 12-lead electrocardiogram<br>Diagnostic Test: heart rate monitor<br>* 24-hour heart rate monitor used to calculate mean heart rate and heart rate variability<br>Diagnostic Test: Autonomic Nervous System (ANS) Activity<br>* Heart Rate Variability (HRV) and Baroreflex sensitivity (BRS): Resting and exercise HRV and BRS calculated from ECG, Dundee Step test and blood pressure measurements.<br>Diagnostic Test: Haemodynamic variables<br>* Cardiac output (CO), stroke volume (SV) and systematic vascular resistance (SVR) will be assessed and calculated using a non-invasive, inert gas re-breathing technique whereby expired gases will be sampled and analysed alongside and blood pressure measurements.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Feasibility of examining autonomic function and related haemodynamic variables in pregnant women with and without inappropriate sinus tachycardia | Number of women in each group who agree to participate in the study | Up to 3 years | 
| Assessment of autonomic function and related haemodynamic variables in pregnant women with and without inappropriate sinus tachycardia | Heart rate variability (HRV) at rest using time and frequency domain (e.g. SDNN ms and LF and HF), combined to give absolute power in ms². | Up to 3 years | 
| Assessment of autonomic function and related haemodynamic variables in pregnant women with and without inappropriate sinus tachycardia | Baroreflex sensitivity (BRS) at rest calculated from the change in systolic pressure and change in R-R interval to give change in pressure per change in RR interval, measured in milliseconds (mmHg/ms) | Up to 3 years | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Assessment of ANS function in pregnant women with and without IST, at rest and during mild exercise | Stroke volume in ml | Up to 3 years | 
| Assessment of ANS function in pregnant women with and without IST, at rest and during mild exercise | Heart Rate Variability during mild exercise (3 minute step test) using time and frequency domain (e.g. SDNN ms and LF and HF), combined to give absolute power in ms². | Up to 3 years | 
| Assessment of ANS function in pregnant women with and without IST, at rest and during mild exercise | Cardiac Output in litres/minute | Up to 3 years | 
| Assessment of ANS function in pregnant women with and without IST, at rest and during mild exercise | Blood Pressure in mm/Hg | Up to 3 years | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Inappropriate Sinus Tachycardia, Pregnancy Related, IST