Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates and Body Position - a Pacemaker Based Study
试验速览
- 阶段
- 不适用
- 状态
- 招募中
- 入组人数
- 25
- 试验地点
- 2
- 主要终点
- Change in cardiac output while atrial pacing at lower and higher rates while supine
研究概览
简要总结
The investigators will seek to determine the effects of different heart rates on both stroke volume and cardiac output using non-invasive hemodynamic assessments. In order to safely manipulate the HR, the investigators will study patients with permanent pacemakers in whom heart rate manipulation can be done in a safe and non-invasive manner.
详细描述
Permanent pacemakers have sometimes been used to treat patients with recurrent vasovagal syncope. This is because patients with vasovagal syncope often experience bradycardia at the time of their syncope. Unfortunately, pacemakers are often ineffective in preventing syncope.
Classical cardiovascular hemodynamics would suggest that increasing the heart rate (HR; via pacemaker) should increase the cardiac output (CO). This is because:
CO = HR x Stroke volume (SV).
The assumption is that the SV is fixed during manipulation of the HR. However, this might not be the case. As the number of beats per minute (HR) increases, the cardiac cycle length (R-R interval [RRI]) shortens, as a function of simple math. This means that the time in cardiac systole shortens, and the time in cardiac diastole shortens. Since cardiac diastole is when the heart fills up with blood, faster HR can be associated with decreased cardiac filling times. This, in turn, could compromise the SV. However, there is a paucity of data as to what happens to SV and CO at different HR. Further, it is possible that these effects will be different when a person is lying down supine versus when a patient is upright (when stroke volume will be lower).
The investigators will seek to determine the effects of different HR on both SV & CO. In order to safely manipulate the HR, they will study patients with permanent pacemakers in whom HR manipulation can be done in a safe and non-invasive manner.
研究设计
- 研究类型
- Interventional
- 分配方式
- Na
- 干预模型
- Single Group
- 主要目的
- Treatment
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 70 Years（Adult, Older Adult）
- 性别
- All
- 接受健康志愿者
- 否
入选标准
- •Age 18-70 years (inclusive)
- •Implanted permanent pacemaker or implanted defibrillator capable of atrial and ventricular pacing
- •LV ejection fraction >50%
排除标准
- •Unable or unwilling to provide informed consent
- •Clinical need for a cardiac resynchronization device
结局指标
主要结局
Change in cardiac output while atrial pacing at lower and higher rates while supine
时间窗: 1 day
Change in cardiac output (CO) when atrial pacing at 80 bpm \& 120 bpm while supine. CO = HR x Stroke volume (SV)
次要结局
- Change in cardiac output at lower and higher ventricular (VVI) paced rates while supine(1 day)
- Change in stroke volume at lower and higher ventricular (VVI) paced rates while tilted up(1 day)
- Change of stroke volume at lower and higher atrial (AAI) paced rates while supine versus while upright(1 day)
- Change of stroke volume at lower and higher ventricular (VVI) paced rates while supine versus while upright(1 day)
- Change of cardiac output at lower and higher atrial (AAI) paced rates while supine versus while upright(1 day)
- Change of cardiac output at lower and higher ventricular (VVI) paced rates while supine versus while upright(1 day)
- Change in stroke volume at lower and higher atrial paced rates while tilted up(1 day)