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Questions tagged [cardiology]

The study of the physiology and pathology of the heart and the cardiovascular system.

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10 views

Understanding the ECG waveform with respect to Lead Positions

I am really confused about the Representation of potential in an ECG graph. First i will ask what is on the vertical axis? (I guess it is electrical potential in millivolts) But again it changes for ...
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40 views

In the PR segment of an ECG, how come there's no current flowing?

I don't really know how to phrase the question, but to put it as clearly as I can, I don't get why it is the P wave "flattens down" when the atria have completely depolarized. I get that the charge is ...
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57 views

Why is there disagreement on the number of surfaces of the human heart?

I am finding that some state that there are 5 and some that say that there are 3. For example, "Cardiology: An Integrated Approach" that was published in 2018 states that There are 3 surfaces of ...
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30 views

How much blood do we have when the heart first starts to beat?

How much blood do we have when the heart beats for the first time? It should be between the third and fourth week of embryonic life.
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Why does a stronger heart cause blood pressure go down

Intuitively, why does a stronger heart cause blood pressure to go down? The answers I've found from a cursory google search seem to indicate that it has to "work less hard" to pump the blood and that ...
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1answer
79 views

Was Dr. Livesey's treatment a valid one in the Treasure Islands?

Here is that incident from Treasure Island by Robert Louis Stevenson, where Billy Bones had a 'minor' heart attack or a stroke (according to R.L. Stevenson). To give a little background about Billy ...
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Correlation seen with low billirubin levels but not the gene that causes Gilbert's syndrome

I was reading the following study on associations between bilirubin and CAD (coronary artery disease). They looked at the bilirubin association, and the genes that cause Gilbert's syndrome, which ...
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1answer
48 views

Frameshift Mutation

With regards to LMNA frameshift mutations further downstream in the tail region, specifically (p.Arg455Gln fs*5) which has yet to be found/recorded in any medical literature...Does anyone have any ...
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1answer
36 views

Why does higher venous volume increase atrial pressure?

If the cardiac output stays the same, then why does higher venous volume increase right atrial pressure? Shouldn't the flow rate be conserved (with a constant cardiac output) so that the venous return ...
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Does increasing contractility increase LV ESP?

I see many PV diagrams showing a negligible difference in the ESP when contractility increases. I'm wondering why this is the case, because if more blood is being pumped out into the aorta, the MAP ...
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8 views

Is atrial natriuretic peptide relased when we drink water?

I know that osmolarity is controlled by the hypothalamus and recover by ADH which reabsorb water. It also can be released when ECV is very low. ECV/salt is controlled by aldosterone/atrial ...
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24 views

Vasoconstriction and blood flow

The resistance in a blood vessel is equal to the pressure difference divided by the blood flow. Let us now say that a sympathomimetic causes vasoconstriction which increases the resistance. Does this ...
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30 views

How does the cardiovascular system improve upon repeated, strenuous exercise?

New here, hopefully this is the right place to post this question. It's widely known that repeated, strenuous aerobic exercise gradually improves the capacity of one's cardiovascular system — $\text{...
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75 views

How to define Bigeminy

Firstly, do cardiologists actually count how many bigeminy when they diagnose? Secondly, since bigeminy only exists when there are recurring pattern, do cardiologists count two or three bigeminy in ...
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1answer
55 views

Can anybody recognize this cardiac waveform? [closed]

Is this an artifact or an arrhythmia?
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1answer
179 views

Difference between Premature Atrial Contraction and Atrial Fibrillation

what is the difference between Premature Atrial Contraction and Atrial Fibrillation. I know that both have irregular heart beat but have normal QRS complex. Both have abnormal or absence P waves but a ...
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1answer
35 views

Definition for different arrhythmia

I am wondering if there is an organization, a document or a research that standardize all the rhythms? Such as describing how long should the ECG be flatline to be considered as asystole? The rhythm I ...
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1answer
221 views

How are monocytes larger than capillaries?

I have read that the average size of a capillary is about 8 micrometers. How is it possible that the 15 micrometer or so monocytes in blood do not block these vessels? https://en.m.wikipedia.org/wiki/...
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32 views

For how long can the heart be in asystole and then restart itself?

The medication Adenosine is used for the treatment of some abnormal heart rhythms. However, according to Wikipedia, it can cause asystole for a few seconds: Because of the effects of adenosine on ...
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28 views

Is the medium which transmits the electrical impulse through the heart different to a nerve?

According to Nerve A nerve is an enclosed, cable-like bundle of nerve fibres called axons Being an Axon An axon (from Greek ἄξων áxōn, axis), or nerve fiber, is a long, slender projection of a ...
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Why does repolarisation of the heart start from the point where depolarisation ends?

Depolarisation moves from the atria to the ventricles and ends near the atrioventricular fibrous tissue after completing a swooping motion However, repolarisation first begins where depolarisation ...
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18 views

what are best methods for mrsa screening in hospital?

methods for screening MRSA are based on PCR (mecA detection) and MRSA latex test and culture. I need to know sensitive, specific and cost-effective methods for diagnosis MRSA infection on one work day ...
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1answer
162 views

Cardiac cycle and atrial contraction

During atrial contraction ("a" in the figure), why does the ventricular pressure match the atrial pressure? The ventricular pressure generally stays the same throughout passive filling until it ...
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1answer
111 views

Is returning cholesterol to the liver really performed by HDL?

Various answers in biology SE, including two quite upvoted ones (1, 2) claim that (in humans) returning cholesterol to the liver is done by HDL. If I understand correctly, Wikipedia's Reverse ...
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1answer
259 views

When endothelial cells in blood vessels (arteries or veins) are damaged, does atheroma form first or blood clot?

I have learnt from Khan Academy's video on atheresclerosis that when the endothelial cells of an artery are damaged, atheroma forms at the site, and if the atheroma’s fibrous cap is ruptured, ...
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1answer
78 views

How do veins's valve pocket sinus tend to become hypoxic?

For context, this question relates to the formation of deep vein thrombosis as I read that hypoxemia in vein can trigger coagulation cascade and cause a thrombus to form in vein. I read that vein's ...
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32 views

Are there toxins that cause heart attack and/or stroke in multiple individuals in short time frames?

Are there any known environmental factors that would cause more than one person to have a heart attack or stroke within a short period of time (e.g. 2-3 months) of one another? I'm particularly ...
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1answer
50 views

Will being very muscular (to the point that one is characterised as obese by BMI) increase blood pressure?

It is widely accepted that obesity/overweight (which I believe refers to people with a high amount of fat cells instead of bodybuilders who weigh a lot due to lots of muscle cells) have higher blood ...
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1answer
36 views

Why does atheroma contain thromplastin/tissue factor?

From my understanding, when the endothelial lining of arteries is damaged, atheroma is formed at the site of the damaged area. If the atheromas is ruptured, thromboplastin contained in atheroma is ...
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1answer
94 views

Alcohol effect on heart and vascular system

How does alcohol weaken heart muscles and why does it increase blood pressure both temporarily and long term? Is the long term effect due to increase of plaque or is it due to other effects?
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1answer
129 views

Can the heart generate its own rhythm independent to the SAN?

My textbook and a revision guide, which I believe is a reinterpretation of the textbook, state that: The SAN initiates waves of excitation that usually override the myogenic action of the cardiac ...
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3answers
202 views

Why do our bodies maintain blood pressure but not the flow rate?

This might be a silly question but i'm not not clear I'm always told that blood pressure is homeostatic parameter and can't not be changed but isn't what important is the flow rate to the organs? ...
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1answer
22 views

The detail about the exact time of heart attack

Storage of cholesterol in coronary artery tends to heart attack. But in which phase heart attack occurs? Why only a definite time is called heart attack? Why this is the extreme point of coronary ...
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1answer
47 views

ECG detection using minimal number of electrodes

Disclaimer: Hello, I'm someone from an electrical engineering background, so this question may sound dumb. I wish to make a wearable ECG monitoring device for arrhythmia detection. Since the device ...
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2answers
324 views

Does blood clot reduce blood flow?

I read that blood clot reduces blood flow from few website and from doing an A level biology question; and if this blood clot is formed in pulmonary thrombosis, this can reduce gas exchange in lung. ...
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87 views

How does alcohol interact with sympathomimetics to affect the cardiovascular system?

There is a fair amount of information on the cardiovascular effects of alcohol, and of sympathomimetics. How do they work? And how do their mechanisms interact? We know that similar pathologies ...
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1answer
166 views

How does the cardiac cycle and electrical activity all relate to blood pressure in the heart? [closed]

I know how the cardiac cycle works and understand the electrical activity in the heart such as the AV nodes, SA nodes and Bundles, but how do they work together in relation to blood pressure?
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65 views

Structure separating the left atrium from the ascending aorta?

With reference to the (adult) anatomy of the human heart: The left atrium (LA) and the proximal part of the ascending aorta (Ao) abut one another, as shown nicely in this image [1]. Is there a name ...
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1answer
178 views

How does vasoconstriction retain heat?

I am reading on vasoconstriction on wikipedia. The article states that: When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular ...
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267 views

What does “dissipated” mean here?

This is the context: You know cardiac muscle cells are small cells relative to skeletal muscle cells, but unlike skeletal muscle cells that are arranged in parallel and their contraction is ...
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69 views

Turbulence in blood

Turbulence in blood flow is known to indicate diseased or obstructed arteries. Techniques to measure turbulence in blood flow are mostly based on turbulence kinetic energy measurments using MRI [e.g., ...
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254 views

Understanding beat annotations of arrhythmia ECG dataset

I'm trying to understand the rhythm changes in the MIT BIH dataset. In annotations, there are 2 main types. Beat annotations and rhythm annotations. Rhythm annotations (aux_notes field) contains ...
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1answer
2k views

Heart rate vs body size

It is known that large animals have lower heart rates (beats per minute) than small animals. Is it the same situation in humans? That is: if we have a group women, about the same age and fitness, ...
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149 views

How to obtain normalised ECG given ECG readings across lead 1, 2, and 3?

I saw this youtube video on ECG readings and cardiac dipole vector locus of the heart across the three leads. Posting screenshots from it: My question is how to obtain the graph (2nd image) from the ...
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1answer
33 views

Using formulas to explain why contraction of blood vessels leads to increased blood pressure

I know, I know this is probably a question too simple to be asked on a forum like biology stack exchange. Problem is, I looked many places and can't seem to find a more mathematical approach to ...
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3answers
673 views

Why is the heart adversely impacted by chronic psychological stress, yet it benefits from routine physical exercise?

Chronic psychological stress is commonly said to be deleterious to the heart, and predispose one to cardiovascular disease. Yet the opposite is said about regular aerobic exercise. Physiologically, ...
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54 views

Pain and Angina Pectoris

What causes pain in an angina pectoris? Ok, heart muscles may lack oxygen, but what is the role of pain here? Is it being beneficial? I'd like to know the physiological process of induction of pain ...
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1answer
393 views

The 4-chambered heart

Birds and humans have a four chambered heart. All animals having 4-chambered hearts are warm-blooded. Why are crocodiles an exception? Why are they cold-blooded even though they have a 4-chambered ...
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1answer
362 views

what is the difference between osciloscope and electrocardiograph?

I am completely confused about these two devices! as far as I know, oscilloscope and electrocardiograph, both, show the heat waves(P, QRS, T) so what is the difference between their job?

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