Cardio formative

Question 1

whilst lying down (in the recumbent position), the heart is situated anterior to which vertebrae?

Answer 1

T5-T8

Question 2

describe gap junctions in cardiac muscle and how these differ from skeletal muscle

Answer 2

myocytes in cardiac muscle are electrically connected via gap junctions acts as a functional syncytium skeletal muscle has no gap junctions

Question 3

out of cardiac and skeletal muscle, which has the shorter depolarising phase of the action potential

Answer 3

action potential is shorter in skeletal muscle

Question 4

why can’t cardiac muscle exhibit tetanus?

Answer 4

long refractory period - can’t have many AP’s one after another

Question 5

do cardiac muscle cells have a stable or unstable resting membrane potential?

Answer 5

at least some cardiac muscle cells have a very unstable resting membrane potential that spontaneously depolarise to threshold and they therefore act as pacemakers

Question 6

During embryological development, which pair of aortic arches give rise to the common carotid arteries?

Answer 6

3rd pair of aortic arches constitutes the commencement of the internal carotid artery, and is therefore named the carotid arch

Question 7

What anatomical features allow arterioles to function as resistance vessels?

Answer 7

They have a relatively narrow lumen and strong muscular wall narrow lumen of arterioles gives them a high resistance. The strong muscular wall is able to contract or relax and change that resistance. That is why it is the arterioles that are used, to control the regional redirection of blood flow through the different vascular beds, and to regulate the total peripheral resistance.

Question 8

In the heart, the fast depolarising phase of the cardiac action potential is caused by the influx of which ions?

Answer 8

Influx of Na+ Why? The resting membrane potential is due to the “leaky” K+ channels which allow K+ ions to flow out down their concentration gradient. Once the membrane reaches the threshold potential, there is a fast depolarisation phase. This phase is due to the opening of the voltage-gated Na+ channels causing a rapid influx of Na+ ions into the cell.

Question 9

what causes the 2nd heart sound

Answer 9

Closure of the semilunar valves (one between L ventricle and aorta and R ventricle and pulmonary artery)

Question 10

what causes the 1st heart sound

Answer 10

Closure of the atrioventricular valves

Question 11

What effect is a heart rate in excess of 150 beats per minute is likely to have on the stroke volume?

Answer 11

Decrease preload and therefore decrease stroke volume Why? The heart fills during diastole. If the heart rate is very fast, the time spent in diastole falls and so the time available for cardiac filling is reduced. This means the preload (load on the heart prior to contraction, related to volume of blood in the heart pre-contraction, known as end-diastolic volume) falls. With smaller preload, Starling’s Law tells us there will be a smaller strength of contraction (all due to that length-tension relationship of striated muscle) so less blood will be ejected. Ie there will be a smaller stroke volume.

Question 12

What effect will activation of beta1-adrenoceptors on cardiac myocytes have on stroke volume?

Answer 12

Increase contractility and therefore increase stroke volume Afterload is not affected because it is related to the total peripheral resistance which is primarily controlled by noradrenaline and adrenaline acting on alpha1-adrenoceptors of the smooth muscle surrounding arterioles. Beta1-adrenoceptors will not affect this.

Question 13

What is the distinguishing feature of the pulmonary circulation?

Answer 13

Pulmonary arterioles constrict in response to local hypoxia ^has the effect of redirecting blood to the better ventilated parts of the lung, and maximising O2 uptake.

Question 14

During exercise, which mechanisms cause an increase in venous pressure, and hence venous return to the heart?

Answer 14

• An increase in the systemic filling pressure
• Contraction of smooth muscle surrounding the veins
• Increased rate and depth of respiration
• Rhythmic contraction of skeletal muscle

they all act to squeeze some of the spare capacitance of blood that is normally present in the venules and veins back towards the heart. Important because it allows the EDV (and therefore preload) to be maintained during exercise despite the reduced filling time with higher heart rates.

Question 15

A 46 year old woman has intermittent rapid regular palpitations that are terminated by the valsalva manoeuvre. She feels well between these episodes. Which is the most likely diagnosis?

Answer 15

Supraventricular tachycardia Why? The Valsalva manoeuvre increases vagal (parasympathetic) tone and the effect at the AV node can be termination of supraventricular tachycardia. Where as atrial fibrillation and ventricular ectopics cause irregular palpitations. Ventricular fibrillation leads to a loss of cardiac output, collapse and death if untreated.

Question 16

A 65 year old woman with hypertension is admitted to the acute medical admissions unit with sudden onset of severe breathlessness, and paroxysmal nocturnal dyspnoea (PND). She is tachycardic with an elevated jugular venous pressure (JVP), crackles in both lung fields to the midzones and significant peripheral oedema. Which is the most appropriate initial drug treatment?

Answer 16

Diuretic Why? PND, elevated JVP, lung field crackles and peripheral oedema all indicative of heart failure. Although ACE inhibitors and beta-blockers are used in chronic heart failure and have been shown to increase survival they are not used in acute heart failure. In this case the patient sounds unwell and diuretic is therefore most appropriate. (As she may also have intestinal oedema which would inhibit absorption of oral diuretics, IV diuretic is most appropriate

Question 17

A 68 year old man presents with exertional angina. Which is the most appropriate treatment to improve symptoms?

Answer 17

Beta blocker negatively inotropic reduce the workload of the heart so reduce oxygen requirements/less ischaemia/ less pain.

Question 18

A 40 year old man is found to have high blood pressure. You believe he may suffer from “white coat hypertension”. Which investigation would confirm this?

Answer 18

24 hour ambulatory blood pressure recording this is done first to confirm hypertension after it is confirmed you look at whether it is primary or secondary to another condition

Question 19

A 26 year old woman has a hot, swollen right leg following a flight from Australia. Ultrasound confirms deep vein thrombosis (DVT) in the right lower limb. Which is the most appropriate initial treatment? A. Aspirin B. Clopidogrel C. Low molecular weight heparin D. Thrombolysis E. Warfarin

Answer 19

Low molecular weight heparin is correct treatment for DVT is anticoagulation to prevent further clot propagation You need to be loaded with warfarin before it has a therapeutic effect therefore it would not be the immediate treatment here

Question 20

A child is born with coarctation of the aorta, short stature, neck webbing and gonadal dysgenesis. Which is the most likely diagnosis?

Answer 20

Turner syndrome

Question 21

A 70 year old man has a three month history of pain in the back of both his calves after walking 100 metres. He is a smoker of 53 pack years. Which is the most likely diagnosis?

Answer 21

Peripheral vascular disease Why? The history is classic for intermittent claudication which is ischaemic pain resulting from exertion of the calf muscles with increased oxygen demand which cannot be met due to atherosclerosis of the supplying arteries. Intermittent claudication is a symptom of peripheral vascular disease

Question 22

A newborn infant with a murmur is found to have an atrio-ventricular septal defect on echocardiography. The baby is hypotonic. Which is the most likely diagnosis?

Answer 22

Down syndrome Reduced tone is also a feature of Down syndrome

Question 23

A 70 year old man presents with an ulcer of his left leg. His sleep is being interrupted by severe leg pain. Which is the most likely cause of his ulcer?

Answer 23

Critical limb ischaemia Why? Pain resulting from inadequate arterial supply is worsened by elevation of the leg and the patient may therefore complain that it is worst when they are lying in their bed. Peripheral arterial disease resulting in pain at rest and with loss of tissue viability (e.g. ulceration) is classed as critical limb ischaemia.

Question 24

Venous and diabetic ulcers and squamous carcinoma all tend to what?

Answer 24

not cause severe pain

Question 25

What is post-phlebitic syndrome

Answer 25

symptoms of chronic venous insufficiency secondary to deep venous thrombosis.

Question 26

A 57 year old woman has a six month history of increasing tiredness, weight gain and significant dizziness whilst performing her activities of daily living. She has no chest pain or syncope but does report worsening of her symptoms over the previous two weeks. She takes bisoprolol 10mg for angina.

Which is the estimated ventricular rate shown in the ECG in diagram below?

Answer 26

150bpm

You were shown two ways of measuring the heart rate from the ECG. The calibration pulse on the left always indicates 0.2 seconds and should be equivalent to one large square.

Knowing that, you could measure the time between two R waves, which gives a cardiac interval of 2 large squares, ie 0.4 seconds. So you could fit 2.5 beats each second, or 60 x 2.5 = 150 beats per minute.

Or, since 5 large squares = 1 second, you can count off 30 large squares (which would be 6 seconds) on the rhythm strip at the bottom, count the R waves in that period, and multiply by 10. This gives 15 in 6 seconds, i.e. 150 in 60 seconds (=1 minute).