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Quantification of the heart rate-independent vasodepressor component in carotid sinus syndrome
R Griebenow1, L Krämer, H M Steffen
1Medizinische Universitätsklinik II, Medizinische Klinik Merheim, Köln.
Insights
Carotid sinus syndrome causes a significant blood pressure drop, especially when standing. While AV-sequential pacing is better than ventricular pacing, it doesn't fully prevent symptoms in most patients.
Area of Science:
- Cardiology
- Autonomic Nervous System Physiology
Background:
- Carotid sinus syndrome (CSS) is characterized by exaggerated responses to carotid sinus stimulation.
- The vasodepressor component of CSS, independent of heart rate changes, is a significant clinical concern.
- Orthostasis (standing) is known to exacerbate autonomic dysfunction.
Purpose of the Study:
- To investigate the heart rate-independent vasodepressor response in CSS patients.
- To compare the effects of ventricular pacing versus AV-sequential pacing on blood pressure during carotid sinus stimulation.
- To assess the impact of posture (supine vs. standing) on these responses.
Main Methods:
- 45 patients with CSS underwent carotid pressure testing.
- Hemodynamic parameters were measured during both ventricular pacing and AV-sequential pacing.
- Tests were performed in both supine and standing positions.
Main Results:
- Carotid pressure testing induced significant systolic and diastolic blood pressure drops in all patients.
- This vasodepressor response was markedly more pronounced in the standing position (orthostasis).
- AV-sequential pacing resulted in higher blood pressure and fewer symptoms compared to ventricular pacing, but did not eliminate symptoms in most patients, especially when standing.
Conclusions:
- A clinically significant, heart rate-independent vasodepressor reaction is common in CSS patients.
- This vasodepressor response has a distinct time course compared to vagally mediated heart rate changes.
- Orthostasis intensifies the vasodepressor reaction, limiting the effectiveness of even hemodynamically favorable pacing strategies in preventing symptoms.
Abstract:
In 45 patients with carotid sinus syndrome, the heart rate-independent vasodepressor component under ventricular and av-sequential pacing of the heart was investigated both in supine and in standing patients. Under both forms of pacing, the carotid pressure determination has led to a marked lowering of systolic and diastolic arterial blood pressure which is significantly more pronounced under orthostasis. The blood pressure values reached both in supine and in standing patients are significantly higher under av-sequential pacing than under ventricular pacing. Accordingly, the proportion of symptomatic patients is less under av-sequential pacing in the supine position (17% versus 29%) and in standing (65% versus 83%). The heart rate-independent vasodepressor reaction is maximal on average between 11 s and 16 s after the beginning of the carotid pressure test and persists for 3 s to 7 s. The blood pressure reaches initial values again after 14 s to 20 s. To summarize, these data document that a clinically relevant heart rate-independent vasodepressor reaction is to be reckoned with in the majority of patients with carotid sinus syndrome. This shows a different time course than the vagally determined effect of the carotid sinus reflex on heart rate. Orthostasis intensifies the vasodepressor reaction so that the hemodynamically more favorable av-sequential pacing which is actually more favorable in hemodynamic terms cannot guarantee freedom from symptoms in the majority of patients in the upright standing position.