Updated: 9/8/2018

Cardiac Cycle

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Snapshot
  • A 15-year-old boy presents to the emergency room after collapsing on the basketball court. His mom reports that he has been pushing himself physically to do well in basketball. She states that he has had several episodes of syncope while playing basketball. There is also a family history of sudden cardiac death in several relatives. On physical exam, the boy has an S4 heart sound and a systolic murmur. (Hypertrophic cardiomyopathy)
Introduction
  • The cardiac cycle is divided into 7 components
  • Atrial systole (1) 
    • atria contract
      • this is the final phase of ventricular filling
      • electrocardiogram (ECG) finding
        • P wave
    • final phase of ventricular filling
      • ECG finding
        • PR interval
  • Isovolumetric contraction (2)
    • period from between mitral valve closure to aortic valve opening
    • ventricles contract and pressure increases
      • ECG finding
        • QRS complex
    • pressure is constant, as all the valves are closed
    • period of highest O2 consumption
  • Systolic ejection
    • period from aortic valve opening to aortic valve closing
    • two phases
      • rapid ejection (3)
        • ventricles contracts and pumps blood into arteries
        • ventricular pressure reaches maximum
        • ECG finding
          • ST segment
      • reduced ejection (4)
        • ventricles pump blood at a slower rate
        • ventricular volume is at its minimum
        • ECG finding
          • T wave
  • Isovolumetric relaxation (5)
    • period from aortic valve closure to mitral valve opening
    • ventricles relax and fill passively with blood
  • Rapid ventricular filling (6)
    • period right after mitral valve opens
  • Reduced ventricular filling, or diastasis (7)
    • period right before mitral valve closes
Heart Sounds
  • S1
    • closure of the mitral and tricuspid valves
    • loudest at mitral area
  • S2
    • closure of aortic and pulmonary valves
    • loudest at left upper sternal border
  • S3       
    • early diastole
    • associated with ↑ filling pressures
      • mitral regurgitation
      • congestive heart failure
      • dilated ventricles
    • normal in children and pregnancy
  • S4
    • late diastole
    • also referred to as “atrial kick”
    • loudest at apex with the patient in left lateral decubitus position
    • associated with ↑ atrial pressure and ventricular hypertrophy
      • left atrium pushes against a stiff and noncompliant left ventricular wall
    • always abnormal
Jugular Venous Pulse (JVP)
  • a wave
    • atrial contraction
    • absent in
      • atrial fibrillation
  • c wave
    • right ventricular contraction
    • tricuspid valve is closed and bulges into atrium
  • x descent
    • tricuspid valve is closed and is displaced downward during rapid ejection phase
    • reduced or absent in
      • tricuspid regurgitation
      • right heart failure
  • v wave
    • ↑ right atrial filling pressures against closed tricuspid valve
  • y descent
    • right atrium empties into right ventricle
    • increased in
      • constrictive pericarditis
    • absent in
      • cardiac tamponade

 

 

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Questions (6)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

(M1.CV.42) Figure A shows a pressure-volume loop for the left ventricle. Which of the following changes on the pressure-volume loop best corresponds to stroke volume? Review Topic

QID: 100558
FIGURES:
1

4 => 1

3%

(2/71)

2

1 => 2

11%

(8/71)

3

3 => 4

48%

(34/71)

4

2 => 3

27%

(19/71)

5

Stroke volume can not be calculated from this diagram

7%

(5/71)

M1

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PREFERRED RESPONSE 3
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(M1.CV.75) A 69-year-old male with a history of well-controlled hypertension, diabetes, and depression presents to his primary care physician for a routine visit. He has no present complaints at this time and states that he has been compliant on all his medications. On exam, the physician appreciates a IV/VI crescendo-decrescendo systolic ejection murmur that is immediately preceded by a click and radiates into the carotids. Which of the following pressure-volume loops corresponds to this patient's condition? Review Topic

QID: 106831
FIGURES:
1

Figure A

8%

(9/109)

2

Figure B

74%

(81/109)

3

Figure C

9%

(10/109)

4

Figure D

6%

(7/109)

5

Figure E

0%

(0/109)

M1

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PREFERRED RESPONSE 2

(M1.CV.75) A 72-year-old female with a history of diabetes, asthma, and uncontrolled hypertension presents to her primary care physician for a routine appointment. She reports that she feels well although she does admit that she has been poorly compliant with the diet and exercise changes her physician prescribed on her prior visit. On exam, the physician hears an extra heart sound in late diastole that immediately precedes S1. This heart sound is most associated with which of the following? Review Topic

QID: 106833
1

Mitral stenosis

11%

(8/71)

2

Ventricular dilation

20%

(14/71)

3

Mitral regurgitation

14%

(10/71)

4

Increased filling pressures

28%

(20/71)

5

High atrial pressure

24%

(17/71)

M1

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PREFERRED RESPONSE 5
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