lecture 12

noninvasive

  1. irregular rhythm

  2. enlargment of the ventricles (right or left)

  3. blocks in the conduction system

  4. if the heart is getting enough oxygen

  5. going through heart attack or had one in the past

whats the underlying cause of most abnormalities in the heart?

  • ischemia (#1) - usually caused by coronary artery disease, also blood clot

  • hypertension - causes remodeling of the heart bc the heart is not working as well

  • degenerative changes with aging - fibrosis (inteferes with conduction system)

exceptions

  • cardiomyopathy (heart not pumping adequetly) - infection, diabetes

  • genetic abnormalities

dilated cardiomyopathy - heart is expanded and doesnt contract properly

  • gene affected is called titin (TTN) - holds myosin molecules to the z lines in sarcomeres

  • impaired sarcomere structure

brugada syndrome - irregular rhythm due to mutations in the fast sodium channel (SCN5A)

long QT syndrome - due to mutations in the fast sodium channel or one of the delayed rectifier potassium channels

  • one of the most common heart abnormalities

  • common in young people

  • delayed repolarization

  • v tach - fast irregular ventricular contraction - pvcs in a row

  • ventricles are just twitching - not pumping (dangerous) → fainting → death

SCN5A - fast Na+ channel, KCNQ1 - delayed rectifier K+ channels

491 = 491 mutations of fast sodium channels in humans

LQT1 and LGT3 bot have a number of mutations

  • 1 is the most common

  • and most common cause of sudden death in young people

beta 1 adrenargic receptor on myocyte

NE binds to it → → adenylyl cyclase → cAMP → PKA

L type calcium channel and delayed rectifier potassium channels

  • both must be activated in coordinated way

  • more ca coming in during plateau, more K+ leaving during repolarization

activate SNS → activate both channels (in coordinated way)

if the delayed rect K+ channel cannot be increased with the sympathetic nerve stimulation → myocytes uncoordinated → irregular rhythym

fast na+ channel

  • normal: opens quickly then inactivates quickly

  • LQT-3: flickers between open and inactivates state → delays repolarization

cardiac output = Q

HR controlled by the SNS and PNS

  1. average pressure in the

preload is the amount of blood in the ventricles before contraction, essentially the stretch of the heart muscle, while afterload is the resistance the heart must overcome to pump blood out, influenced by factors like arterial pressure and vascular tone.

test on single myocyte

different preloads = different stretch

isolated dog heart

actually in viva in human

muscle pump exerts more pressure on venus

afterload is like the weight it has to overcome to contract or something

left to right line is SV