Which diseases present with a variable intensity of S1?
Heart blocks, such as second degree (i.e., Mobitz I or Wenckebach) and third degree:
In second-degree A-V block, there is progressive softening of S1, while S2 remains constant. This is due to the increasing P-R lengthening, until a beat is eventually dropped. It is so typical of Mobitz I that Wenckebach could describe it even before electrocardiogram (ECG) availability.
In third-degree A-V block (typical of Morgagni- Adams-Stokes syndrome), the change in S1 intensity is instead random and chaotic because the atrium and ventricle march to the beat of a different drummer, with rates that are totally independent—when ventricular contraction catches the A-V valves wide apart, S1 booms; when it catches them partially closed, S1 softens. The varying S1 intensity is so typically random to allow the recognition of complete block just on the basis of auscultation
Heart blocks, such as second degree (i.e., Mobitz I or Wenckebach) and third degree:
In second-degree A-V block, there is progressive softening of S1, while S2 remains constant. This is due to the increasing P-R lengthening, until a beat is eventually dropped. It is so typical of Mobitz I that Wenckebach could describe it even before electrocardiogram (ECG) availability.
In third-degree A-V block (typical of Morgagni- Adams-Stokes syndrome), the change in S1 intensity is instead random and chaotic because the atrium and ventricle march to the beat of a different drummer, with rates that are totally independent—when ventricular contraction catches the A-V valves wide apart, S1 booms; when it catches them partially closed, S1 softens. The varying S1 intensity is so typically random to allow the recognition of complete block just on the basis of auscultation