L8 material

whats a heart attack

• occurs when arteries become blocked due to plaque buildup = ASCVD

  • atherosclerotic cardiovascular disease

• high LDL is main driver of ASCVD → CAD, myocardial infarction (MI), angine & coronary artery stenosis

• both genetic & lifestyle factors contribute to cholesterol levels

what speeds up an earlier onset of myocardial infarction

higher cholesterol leads to the speed that plaque builds

Modifiable risk factors

• high BP

• high LDL

• diabetes

• smoking

• obesity

• physical inactivity

Nonmodifiable risk factors

• family history (FHX)

  • <55years father or M 1st relative experiencing HA

  • <65years mother or Fm1st relative experiencing HA

• age

• sex ( F or M)

  • Female post menopause

emerging risk factors

• homocysteine

  • diet deficiencies

• elevated Lp(a) levels

• clotting factors

• hsCRP

• pro-thrombotic factors

• pro-inflammatory factors

what is the underlying cause of most Heart Attacks

• atherosclerosis

  • disease of the coronary arteries that takes several years to ‘usually’ develop

  • combination of genetic & lifestyle factors contribute to cholesterol levels

  • high cholesterol → higher speed plaque builds → early onset of MI

Ischemic Heart (IHD)

an imbalance bt the supply of oxygen and the demand of the myocardium resulting in myocardial ischemia

• loss of ATP, ionic disturbances

Myocardium supply can be affected by

• atheroma

• thrombosis

• spasm

• embolus

Myocardium demand can be affected by

• anemia

• hypertension

• high cardiac output

Common triggers of High Cardiac Output

• anemia: less RBCs → demand faster pumping for O2 delivery

• hyperthyroidism: XS thyroid hormones accelerate metabolism & HR

• Obesity: higher tissue mass & vasodilation increase demand

• sepsis/liver disease: vasodilation & inflammation reduce resistance

High Cardiac Output

reduced systemic vascular resistance or excess O2 consumption activates sympathetic responses, initially compensating but risking eventual systolic failure

• often precedes heart failure from chronic overload

Myocardial Infarction (MI)

blood flow (O2) to an area if the myocardium is blocked off, causing tissue damage

• myocardial cell death (necrosis)

• usually plaque rupture with thrombus

• major adverse CV event (MACE) leading to morbidity,, mortality, & LV remodeling

• 20-60% are silent, atypical, or unrecognized

Angina Pectoris

symptom not disease

• stable - most common

  • triggered by an increase in myocardial demand

  • relieved by rest

• unstable - more frequent

  • prolonged in duration & can occur at rest

• variant - least common

  • random & transient episodes triggered bu vasospasm of the CA

  • more prevalent in women; occurs more often at night

Screening & diagnosis

• electrocardiogram (ECG)

  • measures electrical impulse

• stress test

  • measures blood supply to the heart

• coronary angiography

  • shows specific sites of narrowing in the coronary artery

• blood tests

  • can detect the chemical presence of dying heart cells (troponin, CK, or CK-MB)

Acute Coronary Syndrome (ACS)

• ST waves shows heart’s contraction pattern when it pushes blood out the ventricles

• changes in these waves correspond to type of damage

• determine partial to complete blockage

• unstable angine → No ST elevation MI → STEMI

Coronary revascularization

• restoration of blood flow to ischemic myocardium in obstructive CAD

• main modalities have shared goal of improving perfusion, symptoms & prognosis

  • percutaneous coronary intervention (PCI) (angioplasty ± stent)

  • coronary artery bypass grafting (CABG)

Percutaneous Coronary Intervention (PCI) / angioplasty

• non surgical procedure, uses catheter to place a stent to open the blood vessel in the heart that has been narrowed by plaque build up

• signs/symptoms occur around 75% of blockage

Percutaneous Coronary Intervention (PCI) / angioplasty Imaging

• 3D myocardial perfusion CV magnetic resonance permits whole heart coverage & can establish an estimation of myocardium at risk & ischemic burden

Type of plaque & the Burden (TCFA)

• image of the artery & the percentages related with the type of plaque inside it

• plaque

  • fibrous

  • fibro-fatty

  • lipid rich (necrotic)

  • calcified

Thin-Cap Fibroatheroma (TCFA)

• lipid core >10%

• calcium build up in lumen might not feel differently until demand is created which results in heart attack

• chronic inflammation

  • proteolytic enzymes released from macrophages in lesions → unstable angina

  • establish paradigm of matrix degradation & the lesion instability of TCFA

• Resolution

  • stable plaque is intact with thick fibrous cap; smooth muscle cells (SMC) in a matrix rich in collagen

Coronary Artery Bypass Grafting (CABG)

• surgical “bypass graft” which enables oxygenated blood to reach the myocardium; bypasses the blocked portion of diseased artery

• healthy blood vessel is removed from the leg, arm, or chest replaced the damaged one

• mammary graft often used bc its endothelial layer has less openings, lower intercellular junction permeability, greater anti-thrombotic molecules, & higher endothelial NO production

Mechanism of death from coronary causes

• fatal MI

• pump failure with cardiogenic shock

• lethal arrhythmias

• mechanical complications of MI or progressive ischemic cardiomyopathy

• during pullback from revascularization

Coronary Death

• reflects ultimate failure of coronary perfusion to support myocardial function & electrical stability

Sustained ventricular tachycardia

if rhythm last more than 30s

non-sustained ventricular tachycardia

if the fast rhythm self terminates within 30s

Composite Endpoint

occurrence of any several prespecified events (MI, revascularization, coronary death) counting equally as “an event”

• bundled outcomes - in cardiovascular clinical trials

• boosts event #s for better statistical detection of treatment effects

• rationale:

  • composite endpoints aggregate multiple events, raising total incidents from rare ones like death to 20%+ , enhancing the study trial power & feasibility with smaller samples/shorter durations