- Fri Feb 22, 2013 9:14 pm
I vaguely remembered Valsalva from my medical days . Does this help?
The Valsalva manoeuvre may be used to arrest episodes of supraventricular tachycardia, The manoeuvre can sometimes be used to diagnose heart abnormalities, especially when used in conjunction with echocardiogram. For example, the Valsalva manoeuvre classically increases the intensity of hypertrophic cardiomyopathy murmurs, viz. those of dynamic subvalvular left ventricular outflow obstruction; whereas it decreases the intensity of most other murmurs, including aortic stenosis and atrial septal defect.
The Valsalva manoeuvere works by decreasing preload to the heart. A complementary manoeuvre for differentiating disorders is the Handgrip manoeuvre, which increases afterload.
The Valsalva manoeuvre alters heart rate through sympathetic stimulation (e.g. the accelerator nerve). Neuro-muscular junctions at the sinoatrial node (SAN) release the neurotransmitter norepinephrine(noradrenaline), which increases the SAN's depolarisation rate.
These effects decrease the time between pacemaker action potentials, which results in a faster heartbeat. In later phases of the Valsalva manoeuvre (phases II and III), heart rate is reduced due to parasympathetic interplay.