Pacemaker syndrome pathophysiology
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The loss of physiologic timing of atrial and ventricular contractions, or sometimes called AV dyssynchrony, leads to different mechanisms of symptoms production. This altered ventricular contraction will decrease cardiac output, and in turn, will lead to systemic hypotensive reflex response with varying symptoms.
Pacemaker Syndrome Mechanisms:
AV dyssynchrony leads to various symptoms with different mechanisms of symptom production.
- Loss of AV synchrony
- Valvular incompetence
- Asynchronous ventricular contractions
- Ventriculoatrial conduction
- Echo beats
Loss of Atrial Contraction
Inappropriate pacing in patients with decreased ventricular compliance, which may be caused by diseases such as:
All of the above causes result in loss of atrial contraction and significantly reduces cardiac output because in such cases the atria are required to provide 50% of cardiac output, which is normally only 15% - 25%.
Cannon A Waves
- Atrial contraction against a closed tricuspid valve can cause pulsation in the neck and abdomen, headache, cough, and jaw pain.
Increased Atrial Pressure
- Ventricular pacing is associated with dyssynchrony between the atria and ventricles causing an elevated right and left atrial pressures, as well as elevated pulmonary venous and pulmonary arterial pressures, which can in turn lead to symptomatic pulmonary and hepatic congestion.
Increased Production of Natriuretic Peptides
- Patients with pacemaker syndrome exhibit increased plasma levels of ANP. That's due to increase in left atrial pressure and left ventricular filling pressure, which is due to decreased cardiac output caused by dyssynchrony in atrial and ventricular contraction in ventricle paced rhythms.
- ANP and BNP are potent arterial and venous vasodilators that can override carotid and aortic baroreceptor reflexes attempting to compensate for decreased blood pressure.
- Usually patients with cannon a waves have higher plasma levels of ANP than those without cannon a waves.
- A major cause of AV dyssynchrony is VA conduction.
- VA conduction, sometimes referred to as retrograde conduction, leads to delayed, nonphysiologic timing of atrial contraction in relation to ventricular contraction.
- Nevertheless, many conditions other than VA conduction promote AV dyssynchrony.
- Ventricular paced rhythms cause a reduction in cardiac output by causing a nonphysiologic depolarization of the ventricles.
- Depolarization patterns and contraction are altered when pacemaker leads are placed in the apex of the right ventricle.
- This will further decrease blood pressure and cause a secondary increase in ANP and BNP.
- In patients with heart failure it has been shown that institution of biventricular pacing mode has been associated with a better cardiac output.
- Petersen HH, Videbaek J (1992). "[The pacemaker syndrome]". Ugeskr. Laeg. (in Danish). 154 (38): 2547–51. PMID 1413181. Unknown parameter
- Gross JN, Keltz TN, Cooper JA, Breitbart S, Furman S (1992). "Profound "pacemaker syndrome" in hypertrophic cardiomyopathy". Am. J. Cardiol. 70 (18): 1507–11. doi:10.1016/0002-9149(92)90313-N. PMID 1442632. Unknown parameter
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- Schüller H, Brandt J (1991). "The pacemaker syndrome: old and new causes". Clin Cardiol. 14 (4): 336–40. doi:10.1002/clc.4960140410. PMID 2032410. Unknown parameter
- Ellenbogen KA, Gilligan DM, Wood MA, Morillo C, Barold SS (1997). "The pacemaker syndrome—a matter of definition". Am. J. Cardiol. 79 (9): 1226–9. doi:10.1016/S0002-9149(97)00085-4. PMID 9164889. Unknown parameter
- Theodorakis GN, Panou F, Markianos M, Fragakis N, Livanis EG, Kremastinos DT (1997). "Left atrial function and atrial natriuretic factor/cyclic guanosine monophosphate changes in DDD and VVI pacing modes". Am. J. Cardiol. 79 (3): 366–70. doi:10.1016/S0002-9149(97)89285-5. PMID 9036762. Unknown parameter
- Theodorakis GN, Kremastinos DT, Markianos M, Livanis E, Karavolias G, Toutouzas PK (1992). "Total sympathetic activity and atrial natriuretic factor levels in VVI and DDD pacing with different atrioventricular delays during daily activity and exercise". Eur. Heart J. 13 (11): 1477–81. PMID 1334465. Unknown parameter
- Mollazadeh R, Mohimi L, Zeighami M, Fazelifar A, Haghjoo M (2012). "Hemodynamic effect of atrioventricular and interventricular dyssynchrony in patients with biventricular pacing: Implications for the pacemaker syndrome". J Cardiovasc Dis Res. 3 (3): 200–3. doi:10.4103/0975-3583.98892. PMC 3425026. PMID 22923937. Unknown parameter