Chapter 10. Multiple Choice Questions
I. Answers B, D and E are true statements, whereas A and C are false.
II. Answers A and C are true statements, whereas B, D and E are false.
1. Insufficient cardiac output from the left ventricle. Although the ventricular pressure is drastically increased, the resulting bloodflow is so small that the aortic pressure is insufficient during even light exercise.
2. Stenosis of the aortic orifice is perhaps combined with aortic regurgitation.
3. Such a high ventricular pressure, perhaps maintained over years, is probably related to ventricular dilatation (Starlings law of the heart), and to ventricular hypertrophy with a very thick wall.
1. Aortic stenosis caused by rheumatoid fever and endocarditis is a likely diagnosis.
2. The ECG shows left ventricular hypertrophy with a strain pattern in V4-V6. The strain pattern suggests myocardial ischaemia probably of the inner myocardial fibres, where the nervous supply is scarce.
3. The prognosis depends upon the therapeutic possibilities. Valvotomy may cause temporary relief, but aortic valve replacement with a prosthetic or tissue valve is necessary to accomplish permanent relief from the obstruction. The patient is advised not to compete in strenuous exercise.
1.The mean arterial pressure: (100 + 90/3) = 130 mmHg. An acceptable normal value is (80 + 40/3) = 93 mmHg. The mean pressure of the patient is seriously increased.
2. The WHO limits for normal arterial blood pressure are 165/95 mmHg. The patient has systemic hypertension.
3. Her heart suffers from hypertrophy of the left ventricle. There is no myocardial ischaemia or strain pattern in the ECG.
4. The arterial hypertension distends the arteries, whereby they become much stiffer than normally. Thus a given stroke volume results in a much higher pressure-amplitude than normally. A totally stiff tube would increase the pressure even more.
1. Rheumatic fever.
2. Poisseulle´s law: Resistance is equal to the driving pressure divided by the bloodflow. The cardiac output 2.5 l per min is equal to 42 ml per s. Accordingly, pulmonary vascular resistance (PVR) is (58-28)/42 = 0.7 mmHg*s*ml-1 = 0.7 PRU (Pressure Resistance Units). Normally, PVR is 0.1 PRU, so the patient has a 7-fold rise in PVR.
3. The large pressure gradient over the mitral orifice in early diastole, where the orifice is open, demonstrates the presence of a stenosis in the mitral orifice. The mitral stenosis was already suggested by the diastolic murmur at the apex (the mitral place).
4. The transit time (t) is equal to Volume/Bloodflow: 5000*0.03/2500 = 0.06 min. This is a slow passage, since the normal transit is 1 s.
1.Raynaud´s disease.
2. Cold and other signals to provoke an abnormally high vasoconstrictor tone trigger the cardiovascular control centres of the brain stem. The bloodflow of hands and fingers is dominantly controlled centrally, but also the brain arteries and arterioles are subject to central neural control, although to a much smaller extent.
3. First the skin becomes pale and white from vasoconstriction, due to slow bloodflow, and finally red because of hyperaemia. The vasoconstriction occurs in the digital arteries, arterioles and skin capillaries. A few minutes later the capillary smooth muscle spasm is released due to local vasodilatators, and the capillaries are filled with oxygen poor blood (the skin becomes blue and is still cold). Finally, the arterial and arteriolar constriction is released and the classical physiological reactive hyperaemia occurs, with red, warm fingers and paresthesia (numbness).