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Flashcards in cardio pathophys Deck (390)
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LaPlace's Law

Wall stress = ((pressure x chamber radius)/2x wall thickness)

1

What factors increase cardiac contractility?

Exercise
Increased SS tone
Catecholamines
Increased HR

2

What factors decrease contractility?

Acidosis
Ischemia
SS blockade (Beta Blocker)

3

What is concentric hypertrophy?

Seen w/ high BP
increase in number of sarcomeres laid in parallel -> decreased cavity size and increased wall thickness -> decreased wall stress w/ preserved contractility

4

What is eccentric hypertrophy?

Occurs w/ chronically elevated preload
Increased sarcomeres in series -> increased chamber size + increased wall stress -> increased sarcomeres in parallel
proportional increases in cavity size and wall thickness

5

What is concentric remodelling?

Reversible, physiologic LV hypertrophy seen in athletes.

6

4 ways that IC Ca++ is recovered after cardiomyocyte contraction

1: SERCA - in SR, ATP dependent
2: Na/Ca exchanger - uses Na gradient to move Ca out
3: Plasma membrane Ca++ -ATPase
4: Mitochondrial Ca++ uniporter

7

What is preload?

Passive tension in cardiac myocyte at rest - length of cell prior to contraction

Greater length -> stronger contraction

8

What is afterload?

The force that a muscle cell must overcome in order to contract

9

What is isometric contraction?

Afterload > contraction force
sarcomere does not shorten

10

What is contractility?

contractility = inotropy
intrinsic ability of cardiac myocyte to alter ability to contract independent of preload and afterload

due to changes in biochemical environment of myocyte
due to increased actin-myosin interractions.

11

Stroke Volume

EDV - ESV = SV

12

Ejection Fraction

EF = SV / EDV

13

3 phases of ventricular filling

Early rapid filling
Slow mid-diastolic filling
Rapid filling from atrial contraction

14

2 factors that influence Preload

Venous return (blood volume, venous tone, posture, pericardial constraint, atrial contraction efficacy)
Ventricular compliance

15

What is normal EF? What EF %s indicate mild, moderate, severe dysfunction?

Normal: 55-65%
Mild LV dysfunction: 45-54%
Moderate LV dysfunction: 30-44%
Severe LV dysfunction: <30%

16

2 methods of measuring CO

Thermodilution: most common - cath inserted, cold saline injected in RA, measured in PA, CO is calculated

Fick method: tedious
equation: CO = O2 consumption / AV O2 difference

17

What is a Wood Unit (WU)?

Used in calculations of TPR
WU = (dyne . sec . cm^-5) / 80

18

How is TPR calculated? Normal values?

measure of afterload
Mean pressure difference across vascular bed / mean blood flow
Systemic VR = (MAP - MRAP)/CO. Normal = 13-16 WU
Pulmonary VR = (MPAP - PCWP)/CO. Normal = 0.5-11 WU

19

What is initial treatment for STEMI?

PCI, CABG
If not immediately possible - thrombolytics

20

what anti-ischemic treatments are recommended for early hospital care of ischemic heart disease?

1: oxygen (maintain O2 sat >90%)
2: nitrates (SLx3 or IV for ongoing ischemia, HF, HTN)
3: Oral B-blocker in 1st 24 hrs if no contraindication
4: NDHP Ca++ channel blocker if B-blocker contraindicated
5: ACE inhibitor in 1st 24 hrs for HF or EF <40%
6: Statin

21

What are contraindications for Nitrate use?

Hypotension (present or likely)
Right ventricular infarct
Severe aortic stenosis
PDEi taken in last 24 hours

22

What are indications for Beta blocker use in Ischemic heart disease and what are the preferred agents?

Ongoing chest pain, hypertension or tachycardia not caused by HF

Metoprolol or atenolol are preferred

23

Should a patient w/ MI precipitated by cocaine use be treated with a beta-blocker?

No
Blockade of B2 mediated vasodilation may precipitate coronary artery spasm

24

What patients may receive IV beta blocker?

Patients with ischemic heart disease and significant hypertension
Afib with RVR

25

Contraindications for beta-blocker use

active bronchospasm
hypotension, bradycardia, heart block, pulmonary edema
MI assoc. w/ cocaine use

26

What is the recommended statin in treatment of ischemic heart disease?

Atorvastatin, 80mg / day

27

What studies demonstrated the efficacy of statin treatment in treatment of ischemic heart disease?

PROVEIT-TIMI 22 and MIRACL

28

What is class III therapy for ischemic heart disease?

Contraindicated therapy
-Nitrates if Systolic pressure <90
-Nitrates if Sildenafil or Tadalafil w/in 24 hrs
-Immediate release Ca Channel blockers w/o B-blocker
-IV ACEi
-IV B-blocker if AHF, low output, long PR, 2nd or 3rd deg heart block, asthma or reactive airway disease
-NSAIDs and COX-2 inhibitors

29

What is the mechanism of aspirin's anti-platelet activity?

inhibition of Thromboxane A2 (stimulates platelet aggregation)

Aspirin irreversibly inhibits COX inhibiting PGI2 and TxA2 production.