How does a significant decrease in preload due to severe dehydration affect cardiac output ?

Cardiac output (CO = SV × HR) decreases because reduced venous return leads to lower end-diastolic volume (EDV), which directly reduces stroke volume (SV) via the Frank-Starling mechanism.

Why is the myocardium primarily perfused with oxygenated blood during diastole ?

During systole , the high intramyocardial pressure compresses the coronary vessels. When the aortic valve closes during diastole , the elastic recoil of the aorta maintains perfusion pressure, allowing blood to flow into the coronary arteries.

What is the clinical significance of losing the atrial kick in patients with atrial fibrillation ?

The atrial kick contributes up to 20-30% of ventricular filling. Its loss reduces preload , which can significantly decrease cardiac output , particularly in patients with stiff, non-compliant ventricles (diastolic dysfunction).

Explain the role of afterload in a patient presenting with hypertensive crisis.

Afterload represents the resistance the left ventricle must overcome to eject blood. Elevated afterload increases myocardial oxygen demand and reduces stroke volume , potentially leading to acute heart failure if the heart cannot maintain the pressure gradient.

In the context of the cardiac action potential , what does the absolute refractory period prevent?

It prevents the generation of a second action potential until the cell has sufficiently repolarized, ensuring the heart maintains a rhythmic contraction-relaxation cycle and preventing tetanic contraction .

Why is Lead II the standard choice for continuous cardiac rhythm monitoring?

Lead II aligns most closely with the heart's natural electrical axis (from the SA node to the apex), providing the most prominent, upright P-waves and QRS complexes for reliable rhythm identification.

What is the primary ECG finding that necessitates immediate Code STEMI activation?

The presence of new ST-segment elevation in two or more contiguous leads, indicating acute transmural myocardial injury and the immediate need for reperfusion therapy to save myocardium.

How does CPAP (Continuous Positive Airway Pressure) benefit a patient in acute cardiogenic pulmonary oedema ?

CPAP increases intrathoracic pressure, which decreases venous return (reducing preload ) and reduces the pressure gradient against which the heart pumps (reducing afterload ), while simultaneously improving alveolar gas exchange.

What physiological difference distinguishes systolic heart failure from diastolic heart failure ?

Systolic heart failure is defined by impaired contractility and reduced ejection fraction , while diastolic heart failure is characterized by impaired ventricular relaxation and filling despite a preserved ejection fraction .

Why is the LAD (Left Anterior Descending) artery often referred to as the 'widow-maker'?

The LAD supplies a large portion of the left ventricular myocardium. An occlusion here results in extensive ischemia, frequently leading to profound cardiac output failure or lethal ventricular arrhythmias .

Using the equation $BP = CO \times PVR$, why does a patient in anaphylactic shock experience hypotension?

Anaphylaxis causes massive systemic vasodilation, which drastically reduces peripheral vascular resistance (PVR). Even if cardiac output (CO) is initially maintained, the drop in PVR leads to a precipitous fall in blood pressure.

What is the clinical consequence of third-degree AV block on ventricular pacing?

In third-degree AV block , there is no electrical communication between the atria and ventricles. The ventricles rely on a slow, unreliable escape rhythm, which usually results in inadequate cardiac output and symptomatic bradycardia.

How do you calculate heart rate using the 300-method on an ECG strip?

Divide 300 by the number of large (5mm) squares between consecutive R-waves . This provides an accurate rate calculation for regular rhythms.

What is the mechanism by which myocardial infarction leads to cardiogenic shock ?

Extensive loss of functional myocardium reduces the heart's ability to generate sufficient stroke volume , leading to profound hypotension, inadequate tissue perfusion, and a compensatory (but often maladaptive) increase in afterload .

Why is time = muscle the guiding principle in prehospital STEMI management?

Myocardial cells begin to undergo irreversible necrosis within minutes of sustained ischemia. Early intervention ( PCI or thrombolysis ) restores perfusion, limits the size of the infarct, and significantly improves long-term patient survival.

Cardiovascular Physiology And Clinical Management For Emergency Prehospital Care Flashcards

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Cardiovascular Physiology and Clinical Management for Emergency Prehospital Care

This deck covers essential cardiovascular hemodynamics, ECG interpretation, and clinical management strategies for acute coronary syndromes and heart failure in emergency settings.

15 cards

intermediate

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by @eli_shanna

Q: How does a significant decrease in preload due to severe dehydration affect <strong...

Q: Why is the myocardium primarily perfused with oxygenated blood during diast...

Q: What is the clinical significance of losing the atrial kick in patients with <stron...

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