70 Questions
What is the time period when contraction and tension development occur in the cardiac cycle?
Systole
What happens when the LV pressure exceeds LA pressure but is less than aortic pressure in the cardiac cycle?
Isovolumetric contraction
What is the approximate percentage of ventricular filling accounted for by atrial systole in the cardiac cycle?
10-15%
During which phase of the cardiac cycle does the LV pressure exceed LA pressure, leading to MV closure?
Isovolumetric contraction
When does rapid ejection occur in the cardiac cycle?
When LV pressure exceeds aortic pressure
What does a pressure-volume loop illustrate during one cardiac cycle?
Pressure-volume relationship in the LV
How is stroke volume calculated based on the pressure-volume loop?
$SV = EDV - ESV$
What is the normal ejection fraction range for the left ventricle?
60-70%
What is the volume of blood pumped from the left ventricle per beat?
50-60 mL
During which phase of the cardiac cycle does the LV volume remain unchanged while LV pressure rises rapidly?
Isovolumetric relaxation
Which valvular diseases are associated with concentric hypertrophy? (Select 2.)
Aortic stenosis
Which valvular diseases are associated with eccentric hypertrophy? (Select 2.)
Mitral stenosis
What is the hallmark of dysfunction in the right bundle branch?
Wide and upwardly deflected QRS in lead V1
Which phase of the ventricular muscle action potential is characterized by the upstroke and the opening of fast Na+ channels?
Phase 0
What is the resting membrane potential of the cardiac ventricular muscle?
-90 mV
What does depolarization take place in excitable tissue result in?
Action potential
At what phase of the cardiac action potential does the membrane potential drop below -60mV, allowing a second action potential to be fired with a greater stimulus?
Phase 3
What characterizes the absolute refractory period of the cardiac action potential?
Time during which an action potential may not be evoked, even if elicited by a stimulus at the cellular level
Which type of cell permeability allows potassium to exit the cell during the action potential?
Myocyte permeability to K+ only
What is unique about the cardiac myocyte action potential compared to other cells?
It has a prolonged plateau phase allowing time for contraction.
What differentiates Phase 2 of the ventricular muscle action potential from other phases?
Opening of L-type Ca++ channels
Which phase of the ventricular muscle action potential marks the initiation of contraction?
Phase 2
What is the difference between the resting membrane potential and threshold potential?
The resting membrane potential is higher than threshold potential.
What is the term for the ventricular wall tension at the end of diastole, just before contraction?
Preload
Which factor influences preload by increasing the ventricular wall tension at the end of diastole?
Blood volume
What is the relationship between ventricular end-diastolic volume (EDV) and stroke volume (SV) known as?
Frank-Starling Mechanism
What is the force that the ventricle must overcome to eject its stroke volume known as?
Afterload
What is the intrinsic strength and vigor of the heart’s contraction during systole known as?
Contractility
Which factor is independent of either preload or afterload and represents the intrinsic ability of the myocardium to pump in absence of changes to preload or afterload?
Elastance
What is the period of time when ventricles are relaxed and not contracting known as?
Diastole
What is the time during which left and right ventricles contract and eject blood into aorta and pulmonary artery known as?
Systole
"Wigger's diagram" includes which of the following waves?
"a" wave, "c" wave, "v" wave
What is the term for the electrical and mechanical events taking place from one heartbeat to the next?
Cardiac cycle
Which factor influences preload by increasing the ventricular wall tension at the end of diastole by pressure buildup from venous return before AV valve opens again?
Veinous tone
What is the relationship between ventricular volume and ventricular output known as?
Ventricular Function Curve
What type of hypertrophy is expected in response to regurgitant heart lesions?
Eccentric hypertrophy
Which valve lesion is characterized by thickening of valve leaflets promoting calcification and rigidity?
Mitral stenosis
What is the normal mitral valve area?
$4–6 cm^2$
Which condition causes mitral regurgitation due to abnormalities of the papillary muscles and chordae tendinae?
Acute MI with chordae tendinae rupture
Chronic mitral regurgitation results in which type of left ventricular compensation?
Eccentric hypertrophy
What is the hemodynamic goal for a patient with aortic regurgitation?
Maintain normal to increased preload
Which condition is associated with a long asymptomatic period, progressive eccentric enlargement of the left ventricle, and may lead to CHF and angina?
Aortic stenosis
What type of LV hypertrophy allows the ventricle to maintain stroke volume in aortic stenosis?
$Concentric hypertrophy$
What is the normal valve orifice size for aortic stenosis?
$2.5-3.5 cm^2$
What is the expected change in myocardial O2 supply and heart mass in severe aortic stenosis?
Reduced O2 supply and increased heart mass
What are the hemodynamic goals for aortic valve lesions?
Maintain NSR, increase preload, decrease afterload, moderate increase in heart rate
What type of valve replacement surgery would be appropriate for severe mitral stenosis?
Surgical AVR
What is the primary role of the Bachmann's bundle in the heart's conduction system?
Acting as the preferential path for electrical activation of the left atrium
What allows the spread of action potentials (AP) throughout the cardiac muscle?
Gap junctions interconnecting myocardial cells
What is the function of the AV node in the heart's conduction system?
Serving as the link between atrial and ventricular depolarization
What is the role of Purkinje fibers in the heart's conduction system?
Ensuring a single coordinated contraction of the ventricles
What is a characteristic feature of LBBB (left bundle branch block)?
Blocked impulse in the left ventricle
Which part of the heart is responsible for generating the action potential leading to depolarization of all other cardiac muscle cells?
SA node
What allows electrical excitation to couple with contraction of cardiac muscle in the heart?
Excitation-Contraction coupling
What ensures that right and left atria contract essentially at the same time?
SA node depolarization
What is the role of the middle internodal tract in the heart's conduction system?
Curves behind SVC before descending to AV node
What does the posterior internodal tract do in the heart's conduction system?
Curves behind SVC before descending to AV node
What explains why the inside of the cell is negative in relation to the outside?
Leakage of K+ ions
What happens when serum K+ levels decrease?
The RMP becomes more negative
What is the primary determinant of the resting membrane potential (RMP)?
Potassium ions (K+)
What happens when the RMP approaches the threshold potential?
Voltage-gated Na+ channels open and Na+ conductance increases
What is the purpose of the Na+/K+ ATPase pump?
Restores ionic balance towards RMP
What is the higher resting membrane potential of the SA node compared to ventricular muscle?
-60mV
What is responsible for slow depolarization in the SA node, known as 'pacemaker potential'?
Increased Na+ permeability
What occurs when SA nodal disease impairs its ability to function as the heart’s dominant pacemaker?
Atrial pacemakers assume pacemaker responsibility
What is characteristic of inherent rates of conduction in Purkinje fibers?
40-60 bpm
What condition can impact transmission of action potentials from atria to ventricles?
Second-degree AV block
What determines preload or end-diastolic volume (EDV)?
The filling pressure of the heart at the end of diastole.
What is responsible for controlling stroke volume?
Preload / End-Diastolic Volume (EDV)
What controls heart rate?
The HR may be higher or lower due to constant influence of nerves and hormones
Test your knowledge of cardiac function, systolic pressure, and the impact of systolic pressure on stroke volume and contractility. Explore the effect of sympathetic activity and pharmacologic agents on inherent strength and vigor of the heart's contraction during systole.
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