Cardiovascular alterations Ch 12

ANA: The sympathetic nervous system releases norepinephrine, which has alpha- and beta- adrenergic effects. Alpha-adrenergic effects cause arterial vasoconstriction. Beta-adrenergic effects increase sinus node discharge (positive chronotropic), increase the force of contraction (positive inotropic), and accelerate the AV conduction time (positive dromotropic). The parasympathetic nervous system releases acetylcholine through stimulation of the vagus nerve. It causes a decrease in the sinus node discharge and slows conduction through the AV node. The blood supply to the myocardium is derived from the coronary arteries NOT ON EXAM S1: best heard at the apex of the heart (fifth intercostal space, left midclavicular line) and represents the beginning of ventricular systole. S2: It has been described as “dub” and is caused by closure of the pulmonic and aortic valves. It is best heard at the second intercostal space at the left or right sternal border and represents the beginning of ventricular diastole. The first and second heart sounds are best heard with the diaphragm of the stethoscope. S3: S3 or ventricular or protodiastolic gallop, is a normal variant in young adults, but usually abnormal the older adult. The sound is caused by rapid left ventricular filling and may be produced at the time when the heart is already overfilled or poorly compliant. The S3 sound is low pitched and can best be heard with the bell of the stethoscope at the fifth intercostal space, at the left midclavicular line. It occurs immediately after S 2. Together with S1 and S 2, S 3 produces a “lub-dubba” or “ken-tuk'e” sound. S3 is often heard in patients with HF or fluid overload. S4: Presystolic or atrial gallop, is produced from atrial contraction that is more forceful than normal. Together with S 1 and S 2, S4produces a “te-lubb-dubb” or “ten'-ne-see” sound. S4 can be normal in elderly patients, but it is often heard after an acute myocardial infarction (AMI), when the atria contract more forcefully against ventricles distended with blood. In the severely failing heart, all four sounds (S4, S1, S2 , and S 3) may be heard, producing a “gallop” rhythm (quadruple gallop), so named because it sounds like the hoof beats of a galloping horse.