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Haemodynamic effect of atrail triggered versus fixed rate pacing at rest and during exercise in complete heart block
Insights
Atrial triggered pacemakers (ATP) improve cardiac output and oxygen transport during exercise in patients with complete AV block compared to fixed rate pacemakers (FRP). This enhancement is particularly beneficial for younger patients and those with low ventricular compliance.
Area of Science:
- Cardiology
- Biomedical Engineering
Background:
- Complete atrioventricular (AV) block significantly impairs cardiac function.
- Pacemaker therapy is essential for managing AV block, but pacing mode can affect hemodynamics.
Purpose of the Study:
- To compare central hemodynamics at rest and during exercise between fixed rate pacing (FRP) and atrial triggered pacing (ATP) in patients with complete AV block.
- To evaluate the impact of synchronized atrial contraction on ventricular filling and cardiac output.
Main Methods:
- Hemodynamic parameters (pressures, cardiac output) were measured during heart catheterization in 25 patients with complete AV block.
- Patients were studied with both FRP and ATP modes, including rest and exercise conditions.
- Atrial triggering for ATP was achieved using an atrial electrode placed via mediastinoscopy.
Main Results:
- Cardiac output (Q) was significantly higher with ATP compared to FRP at rest (10-18%) and during exercise (8-20%).
- Stroke volume (SV) was similar at rest but significantly larger with FRP during exercise in one series.
- Left ventricular (LV) filling pressure was lower at rest with ATP, with no significant difference during exercise.
Conclusions:
- Atrial triggered pacing (ATP) enhances cardiac output and oxygen transport capacity during exercise in patients with complete AV block.
- The benefits of ATP may be more pronounced in younger patients and those with reduced ventricular myocardial compliance.
- ATP optimizes ventricular filling through synchronized atrial contraction, leading to improved hemodynamic performance.
Abstract:
The central haemodynamics at rest and during exercise have been studied in 25 patients with complete AV block who were treated with fixed rate (FRP) and atrial triggered pacemakers (ATP). The aim of the investigation has been to study the effect of a synchronized atrial contraction for the filling of the ventricles and for the cardiac output (Q). Pressures and Q have been determined during heart catheterization. The P wave for triggering the atrial synchronized pacemaker has been obtained with an electrode in close contact with the atria, introduced by means of mediastinoscopy. The study consists of two series. In the first series (12 patients) the central haemodynamics were recorded with each patient connected first the FRP (about 70 impulses/min) and later to the ATP. Most patients were studied both at rest and during exercise, the work loads being identical with both types of pacemakers. Q at rest is 10% higher with ATP (p less than 0.02) than with FRP and during exercise 20% higher with ATP (p less than 0.01). Stroke volume (SV) at rest is equal with both types of pacemakers, but significantly larger with FRP during work (p less 0.001). The left ventricular (LV) filling pressure is significantly lower (p less than 0.01) with ATP at rest, but not during exercise (p less than 0.8). In the second series 13 patients were studied at rest and during exercise. The recordings of pressures and Q were first performed with the patient on ATP. After 30 min rest an identical study was performed with the patient connected to FRP, the rate of which was matched (FRPm) to that previously recorded with ATP. Q at rest is 18% higher (p less than 0.01) with ATP than with FRPm and during work 8% higher (p less than 0.05) with ATP. SV at rest is significantly larger (p less than 0.01) with ATP than with FRPm, whereas during exercise no significant difference is observed between the two types of pacemakers. LV filling pressure at rest is significantly lower on the 5% level with ATP; during exercise no significant difference is observed. The investigation shows that in many patients, especially younger ones, treatment with ATP makes it possible to obtain a larger Q during exercise, and thus to increase the oxygen transporting capacity of the circulation. This benefical effect may be more pronounced in patients with low compliance of the ventricular myocardium.