CARDIOVASCULAR REVIEW

Coronary artery anatomy

RAC: (Right Artery Coronary)

          1) Marginal artery—supplies right ventricle.

          2) PD (posterior descending/interventricular artery)—supplies posterior septum.

          In the majority of cases, the SA and AV nodes are supplied by RCA. The 80% of the time, the RAC supplies the inferior portion of the left ventricle via the PD artery, one 20%, the PD arises from CFX.

LCA: (Left Artery Coronary)

          1)  Left anterior descending artery (LAD)—supplies apex and anterior interventricular septum.

          2) Circumflex artery (CFX)—supplies posterior left ventricle.

Coronary artery occlusion most commonly occurs in the LAD.

Coronary arteries fill during diastole.

The most posterior part of the heart is the left atrium; enlargement can cause dysphagia, due to compression of the esophageal nerve, or hoarseness due to compression of the recurrent laryngeal nerve, a branch of the vagus.

Auscultation of the heart.

Aortic area: Systolic murmur: Aortic stenosis.

                                                 Flow murmur.

                                                 Aortic valve sclerosis.

Pulmonic area: Systolic ejection murmur:

                                                 Pulmonic stenosis.

                                                 Flow murmur (e.g. atrial septal defect).

Tricuspid area: Pansystolic murmur:

                                                 Tricuspid regurgitation.

                                                  Ventricular septal defect.

                         Diastolic murmur:

                                                  Tricuspid stenosis.

                                                  Atrial septal defect.

Mitral area: Systolic murmur:  Mitral regurgitation.

                   Diastolic murmur: Mitral stenosis.

Left sternal border: Systolic murmur:

                                                  Hypertrophic cardiomyopathy.

                                Diastolic murmur:

                                                  Aortic regurgitation.

                                                  Pulmonic regurgitation.

Cardiovascular physiology.

Cardiac output (CO) = stroke volume (SV) x heart rate (HR)

Fick principle:

CO =                 rate of O2 consumption

          Arterial O2 content – venous O2 content

MAP (mean arterial pressure)

TPR (total peripheral resistance)

MAP = CO x TPR

MAP = 2/3 diastolic pressure + 1/3 systolic pressure

Pulse pressure =systolic pressure – diastolic pressure

Pulse pressure is proportional to stroke volume.

SV = CO = EDV – ESV

          HR

During the exercise, CO increase initially as a result of an increase in SV. After prolonged exercise, CO increase as a result of an increase in HR.

If HR is too high, diastolic filling is incomplete and CO decrease, e.g. ventricular tachycardia.

Stroke volume is affected by contractility, afterload, and preload. When increase preload, decrease afterload, or increase the contractility, the stroke volume increase.

Contractility and SV increase with:

1)      Catecholamines (increase activity of Ca 2+ pump in sarcoplasmic reticulum).

2)      Increases intracellular calcium.

3)      Decrease extracellular sodium (decrease activity of Na+/Ca2+ exchanger).

4)      Digitalis (increase intracellular sodium, resulting in increase calcium).

Contractility and SV decrease with:

1)      β1 blockade.  

2)      Heart failure.

3)      Acidosis

4)      Hypoxia/Hypercapnia.

5)      Non-dihydropyridine Ca2+ channel blocker.

    

SV increases in anxiety, exercise, and pregnancy.

A failing heart has decrease SV.

Myocardial O2 demand is increases by:

1)      ↑ afterload

2)      ↑ contractility

3)      ↑ heart rate

4)      ↑ heart size

Preload = ventricular EDV.

Afterload = MAP and proportional to peripheral resistance.

Preload increases with exercise (slightly),↑ blood volume (overtransfusion), and excitement (sympathetics).

Preload pumps up the heart.

Force of contraction is proportional to initial length of cardiac muscle fiber (preload).

Ejection fraction (EF).

EF is an index of ventricular contractility; it is normally ≥ 55%.

EF = SV        = EDV – ESV  

       EDV              EDV

The resistance is directly proportional to viscosity, and inversely proportional to the radius of the 4^th power. This means that is the radius of a blood vessel doubles by vasodilatation, then the flow will increases 16 fold. On the other hand, is the radius of the vessel is reduce in half, by vasoconstriction, then the blood flow will be reduced16 fold.

The viscosity depends mostly on hematocrit.

Viscosity increase in:

1)      Polycythemia.

2)      Hyperproteinemic state.

3)      Hereditary Spherocytosis.

Cardiac cycle.

Phases—left ventricle:

1)      Isovolumetric contraction; period between mitral valve closure and aortic valve opening (highest O2 consumption).

2)      Systolic ejection: period between aortic valve opening and closing.

3)      Isovolumetric relaxation: period between aortic valve closing and mitral valve opening.

4)      Rapid filling: period just after mitral valve opening.

5)      Reduced filling: period just before mitral valve closure.