Cardiovascular lecture notes - Revision history

Admin: moved Cardiovascular lectures to Cardiovascular lecture notes

Admin — Wed, 17 Mar 2010 14:22:28 GMT

moved Cardiovascular lectures to Cardiovascular lecture notes

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Revision as of 14:22, 17 March 2010

149.166.132.172: /* Pacemaker cells */

149.166.132.172 — Mon, 08 Mar 2010 19:41:30 GMT

Pacemaker cells

← Older revision		Revision as of 19:41, 8 March 2010
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	*-40 mV is the threshold in pacemaker cells.		*-40 mV is the threshold in pacemaker cells.
	*After an action potential, the potential drops below threshold and then starts leaking back toward threshold such that another action potential is fired.		*After an action potential, the potential drops below threshold and then starts leaking back toward threshold such that another action potential is fired.
-	*The '''depolarization drift''' comes from the flow of ~~ions~~ through the desmosomes.	+	*The '''depolarization drift''' comes from the flow of Na+ through the desmosomes.
	*Upon reaching threshold, Ca++ channels (voltage sensitive) open up and Ca++ rushes into the pacemaker cells. This happens very quickly and drives the potential inside the pacemaker cell well into the positive range.		*Upon reaching threshold, Ca++ channels (voltage sensitive) open up and Ca++ rushes into the pacemaker cells. This happens very quickly and drives the potential inside the pacemaker cell well into the positive range.
	*Then polarization is maintained by slow calcium channels that open late and stay open for a longer time.		*Then polarization is maintained by slow calcium channels that open late and stay open for a longer time.

149.166.219.148: /* Theoretical combination therapy */

149.166.219.148 — Mon, 08 Mar 2010 00:15:38 GMT

Theoretical combination therapy

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	**Sometimes the heart can repair itself to the point that the LVAD can be removed.		**Sometimes the heart can repair itself to the point that the LVAD can be removed.
	*Other therapies may include:		*Other therapies may include:
-	**Beta agonists like clenbuterol which would cause the cardiac cells to hypertrophy (through ~~increases~~ stimulation by the sympathetic system).	+	**Beta agonists like clenbuterol which would cause the cardiac cells to hypertrophy (through increased stimulation by the sympathetic system).
	**Agents that stimulate coronary vessel re-growth.		**Agents that stimulate coronary vessel re-growth.
	*The goal is to allow the heart to repair itself.		*The goal is to allow the heart to repair itself.

149.166.219.148: /* The next generation of artificial hearts */

149.166.219.148 — Mon, 08 Mar 2010 00:14:30 GMT

The next generation of artificial hearts

← Older revision		Revision as of 00:14, 8 March 2010
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	*These are connected to the bottom of the ventricle and pump the blood up into the aorta.		*These are connected to the bottom of the ventricle and pump the blood up into the aorta.
	*The grapefruit sized machine is anchored just below the diaphragm.		*The grapefruit sized machine is anchored just below the diaphragm.
-	*~~Now there is lots~~ of ~~external stuff~~.	+	*Nowadays we decrease the size of the internal unit by engineering some things (like the battery) to remain outside the patient.
-	*There is still a risk of infection.	+	*There is still a risk of infection because of the outside-inside interface.
	*Blood clotting is controlled by using pig tissues instead of artificial tissues.		*Blood clotting is controlled by using pig tissues instead of artificial tissues.
	*Biggest problem with the HeartMate is the size.		*Biggest problem with the HeartMate is the size.
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	**This will generate no beat and we thought this would be an issue but it isn't.		**This will generate no beat and we thought this would be an issue but it isn't.
	**The internal / external interface is still a problem for infections and such. We're working on electrical field transfer of power.		**The internal / external interface is still a problem for infections and such. We're working on electrical field transfer of power.
-	**One ~~pt.~~ has made a transatlantic trip and lived 2 years.	+	**One patient has made a transatlantic trip and lived 2 years with one of these devices.

	**In January of 2010, the HeartMate II was approved for long-term treatment of heart failure.		**In January of 2010, the HeartMate II was approved for long-term treatment of heart failure.

149.166.219.148: /* Article: New directions in cardiac transplantation */

149.166.219.148 — Mon, 08 Mar 2010 00:11:07 GMT

Article: New directions in cardiac transplantation

149.166.219.148: /* Treatments for heart problems */

149.166.219.148 — Sun, 07 Mar 2010 23:53:55 GMT

Treatments for heart problems

149.166.219.148: /* Heart rate, physical changes */

149.166.219.148 — Sun, 07 Mar 2010 23:48:20 GMT

Heart rate, physical changes

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	===Heart rate, physical changes===		===Heart rate, physical changes===
	*Age		*Age
-	**Fetal is much higher.	+	**Fetal heart rate is much higher.
-	*Gender (25 ~~yos~~ with ideal weight):	+	*Gender:
-	**Women faster than men~~, fetus~~ much faster than women.	+	**We consider the standard measurements on 25 year olds with ideal weight.
-	*Exercise increases HR ~~b/c~~ of sympathetic stimulation.	+	**Women have faster heart rates than men.
-	*Temperature decreases HR by slowing rate of depolarization of pacemaker cells.	+	**Fetuses have a much faster heart rate than women.
		+	*Exercise increases HR because of sympathetic stimulation.
		+	*Temperature decreases one's HR by slowing the rate of depolarization of pacemaker cells.

	===Cardiac output and energy consumption===		===Cardiac output and energy consumption===

149.166.219.148: /* Cardiac output */

149.166.219.148 — Sun, 07 Mar 2010 23:38:03 GMT

Cardiac output

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	*The cardiac output (CO) is a measure of the amount of blood pumped out of one side of the heart in one minute.		*The cardiac output (CO) is a measure of the amount of blood pumped out of one side of the heart in one minute.
	**Remember, however, that both ventricles have to pump the same volume of blood.		**Remember, however, that both ventricles have to pump the same volume of blood.
-	*CO = heart rate x stroke ~~volumen~~	+	*CO = heart rate x stroke volume
-	*Normal: 6000ml / ~~minu~~ = 75 beats / min x 80 ml / beat.	+	*Normal: 6000ml / min = 75 beats / min x 80 ml / beat.
-	*This can be increased 3 fold upon need.	+	*This can be increased 3-fold upon need.
	*Both heart rate and stroke volume are the function of several different parameters.		*Both heart rate and stroke volume are the function of several different parameters.

	=====Stroke volume=====		=====Stroke volume=====
-	*~~Remember that there is about 50ml left in the left ventricle at the end of the stroke.~~	+	*Stroke volume = end diastolic volume - end systolic volume.
-	*At rest, you pump out of the ventricle 60% of the blood that was in the ventricle at the end of relaxation.	+
-	*SV = end diastolic volume - end systolic volume.	+
	*End systolic volume is the volume of blood left in the ventricle after the contraction.		*End systolic volume is the volume of blood left in the ventricle after the contraction.
		+	**Remember that there is about 50ml left in the left ventricle at the end of the stroke; this is called the end systolic volume.
	*End diastolic volume is the amount of blood in the ventricle after diastole (relaxation).		*End diastolic volume is the amount of blood in the ventricle after diastole (relaxation).
-	*Frank-Starling ~~law of the heart~~:	+	*At rest, you pump out of the ventricle 60% of the blood that was in the ventricle at the end of relaxation (the end diastolic volume). This 60% is the stroke volume.
		+
		+	*Frank-Starling principle:
	**There is a proportional relationship between the diastolic volume of the heart and the stroke volume."		**There is a proportional relationship between the diastolic volume of the heart and the stroke volume."
-	**That is, the heart will pump whatever it receives within limits.	+	**That is, the heart will pump whatever it receives (within limits).

	*Preload:		*Preload:
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	**So, a healthy heart can pump all that it is given (within normal bounds).		**So, a healthy heart can pump all that it is given (within normal bounds).
	**Things that can increase preload:		**Things that can increase preload:
-	***The speed of the venus return can increase ~~cardiact~~ output.	+	***The speed of the venus return can increase cardiac output.
-	***An ~~increase~~ blood volume.	+	***An increased blood volume.
-	***~~Increase in~~ heart rate.	+	***Increased heart rate.
	***Cellular hypertrophy: each cardiomyocyte generates more contractile proteins when there is extra strain on the cells. Note that myocytes do not divide!		***Cellular hypertrophy: each cardiomyocyte generates more contractile proteins when there is extra strain on the cells. Note that myocytes do not divide!
	****Occurs in athletes, when there are blockages, and when you have heart defects like a messed up valve.		****Occurs in athletes, when there are blockages, and when you have heart defects like a messed up valve.
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	***Acidosis, increased extracellular K+, and calcium channel blockers can all decrease contractility of the heart.		***Acidosis, increased extracellular K+, and calcium channel blockers can all decrease contractility of the heart.
	****Calcium channel blockers are used to decrease blood pressure.		****Calcium channel blockers are used to decrease blood pressure.
-	**~~Parasympathetic~~ can decrease contractility and heart rate.	+	**The parasympathetic system can decrease contractility and heart rate.
-	***Acetylcholine decreases contractility by ~~increase~~ parasympathetic signaling.	+	***Acetylcholine decreases contractility by increasing parasympathetic signaling.

	*Afterload		*Afterload

Admin: /* Electrical activation of the heart */

Admin — Sun, 07 Mar 2010 21:37:29 GMT

Electrical activation of the heart

Admin: /* Electrical characterisitcs of the heart */

Admin — Sun, 07 Mar 2010 21:12:49 GMT

Electrical characterisitcs of the heart

← Older revision		Revision as of 21:12, 7 March 2010
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	*If the heart is otherwise healthy, you can cut the nerves and heart will keep on beating.		*If the heart is otherwise healthy, you can cut the nerves and heart will keep on beating.
	*If you take it out of the body (and maintain the temperature) it will start beating faster. The innervation actually slows down the heart beat.		*If you take it out of the body (and maintain the temperature) it will start beating faster. The innervation actually slows down the heart beat.
-	*Thus, when you take the heart out, you put it on ice. ~~What? No!~~	+	*Thus, when you take the heart out, you put it on ice.
	*The stimulus for beating comes from the pacemaker cell.		*The stimulus for beating comes from the pacemaker cell.
	*There are multiple cells that can do this, but the one that fires first wins. The others can take over if need be.		*There are multiple cells that can do this, but the one that fires first wins. The others can take over if need be.
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	*The parasympathetic system slows the heart rate whereas the sympathetic nervous system increases the heart rate.		*The parasympathetic system slows the heart rate whereas the sympathetic nervous system increases the heart rate.
	*Normally the parasympathetic system dominates.		*Normally the parasympathetic system dominates.
-	*First the electrical activity spreads over the atrium, then reconvenes at the AV node, then spreads down to the tip of the heart via the Purkinje fibers.	+	*First, the electrical activity spreads from the SA node over the atrium, then it reconvenes at the AV node, then it spreads down to the tip of the heart via the Purkinje fibers.

	====Pacemaker cells====		====Pacemaker cells====
-	*Action potentials in nerves ~~happen~~ really fast, much faster than in cardiac muscle.	+	*Action potentials through nerves travel really fast--much faster than through cardiac muscle.
-	*All cells have a spontaneous potential difference measured in volts. The outside of the cell is always greater in charge, so the inside is always negative.	+	*All cells of the body have a spontaneous potential difference measured in volts.
-	*Each tissue type has different resting potentials. In pacemaker cells it is -40 ~~volts~~ (that is, -4o inside compared to outside).	+	**The outside of the cell is always greater in charge, so the inside is always negative.
-	*-40 is the threshold in pacemaker cells.	+	*Each tissue type has different resting potentials.
-	*After a potential, the potential drops below threshold and then starts leaking back toward threshold~~, then~~ another action potential is fired.	+	**In pacemaker cells it is -40 millivolts (that is, -40 inside compared to outside).
		+	*-40 mV is the threshold in pacemaker cells.
		+	*After an action potential, the potential drops below threshold and then starts leaking back toward threshold such that another action potential is fired.
	*The '''depolarization drift''' comes from the flow of ions through the desmosomes.		*The '''depolarization drift''' comes from the flow of ions through the desmosomes.
	*Upon reaching threshold, Ca++ channels (voltage sensitive) open up and Ca++ rushes into the pacemaker cells. This happens very quickly and drives the potential inside the pacemaker cell well into the positive range.		*Upon reaching threshold, Ca++ channels (voltage sensitive) open up and Ca++ rushes into the pacemaker cells. This happens very quickly and drives the potential inside the pacemaker cell well into the positive range.
-	*Then repolarization is achieved through potassium channels ~~which allow~~ potassium to ~~rush~~ out of the cell driving the potential back to the negatives.	+	*Then polarization is maintained by slow calcium channels that open late and stay open for a longer time.
-	*How often this occurs determines how often the heart beats.	+	*Then a nearly neutral level of polarization is maintained as potassium channels are opened such that Ca++ is coming in and K+ is going out.
		+	*Then repolarization is achieved through the previously mentioned potassium channels remaining open while the slow calcium channels close, thus allowing potassium to continue out of the cell driving the potential back to the negatives.
		+	*How often this whole process occurs determines how often the heart beats.
	*Normal heart beat is about 70 bpm (3 billion action potentials in 70 years).		*Normal heart beat is about 70 bpm (3 billion action potentials in 70 years).

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	*The autorythmicity is about 90-100.		*The autorythmicity is about 90-100.
	*Neurotransmitters slow the heart rate (those from the parasympathetic system).		*Neurotransmitters slow the heart rate (those from the parasympathetic system).
-	*These NTs cause an ~~increase~~ permiability to potassium which drives the refractory polarization to a lower (more negative) number ~~and then~~ it will take a longer time for enough Na+ to leak in to reach threshold.	+	*These NTs cause an increased permiability to potassium which drives the refractory polarization to a lower (more negative) number such that it will take a longer time for enough Na+ to leak in to reach threshold.
-	*The sympathic system affects both the CA++ channels (makes them faster) and the repolarization.... we'll come back to it.	+	*The sympathic system affects both the Ca++ channels (makes them faster) and the repolarization.... we'll come back to it.

	====Alternate pacemakers====		====Alternate pacemakers====
	*If you lose all the cells in the SA node, the AV node can take over.		*If you lose all the cells in the SA node, the AV node can take over.
-	*You can survive without the atria working but you have ~~to have the~~ ventricles ~~working~~.	+	*You can survive without the atria working but you must have functional ventricles.
	*There are ventricle pacemakers that can take over if you lose the AV node, too, but they are pretty slow (30 bpm) so you're in trouble.		*There are ventricle pacemakers that can take over if you lose the AV node, too, but they are pretty slow (30 bpm) so you're in trouble.
	If the SA node is lost, do the atria still contract?		If the SA node is lost, do the atria still contract?

← Older revision		Revision as of 00:11, 8 March 2010
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	=====Article: New directions in cardiac transplantation=====		=====Article: New directions in cardiac transplantation=====
-	*Summary of > 30 years of clinical ~~practical~~ and some of the new directions that are contributing to ...	+	*Summary of > 30 years of clinical results and some of the new directions that are contributing to successful heart transplants.
	*Read the first half of the article.		*Read the first half of the article.
-	*They studied the mortality in the 90 days post-op and showed that transplants mortality rates are decreasing.	+	*They studied the mortality in the 90 days post-op and showed that transplants mortality rates are decreasing (even though the donors are older, the donor organs have longer ischemic times, and the recipients have more complicated conditions of increased intensity).
	*They also addressed who are good candidates for hearts:		*They also addressed who are good candidates for hearts:
	**In the first two decades of heart transplants we didn't consider people with high age, diabetes, kidney or liver disease, HIV, or hepatitis.		**In the first two decades of heart transplants we didn't consider people with high age, diabetes, kidney or liver disease, HIV, or hepatitis.
	*Ethical issues:		*Ethical issues:
	**Who should get the heart and who shouldn't? Age, weight?		**Who should get the heart and who shouldn't? Age, weight?
-	**Should incurable illnesses ~~be transplanted~~?	+	**Should people with incurable illnesses get transplants?
	**Should elderly patients get young hearts because it will likely outlast the recipient.		**Should elderly patients get young hearts because it will likely outlast the recipient.
	*Interesting scientific notes:		*Interesting scientific notes:
	**Introduced the idea of using a ventricular assist device, which has increased survival both by keeping the patient alive until a donor is found and aiding in survival after transplantation.		**Introduced the idea of using a ventricular assist device, which has increased survival both by keeping the patient alive until a donor is found and aiding in survival after transplantation.
-	**In infants, you don't have to match the ABO blood groups because they have low levels of anti-A and anti-B antibodies. They also have an incompetent complement system.	+	**In infants, you don't have to match the ABO blood groups because they have low levels of anti-A and anti-B antibodies in their serum. They also have an incompetent complement system until 12-14 months, such that they cannot reject the organ as well as someone with a full complement cascade.

	====Artificial hearts====		====Artificial hearts====

← Older revision		Revision as of 23:53, 7 March 2010
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	*Cholesterol lower agents		*Cholesterol lower agents
	*Beta blockers - block sympathetic nervous system - slow HR and force of contraction.		*Beta blockers - block sympathetic nervous system - slow HR and force of contraction.
-	*Ca+ channel blockers - mainly on vessels~~, reduces resistance~~ by opening vessels	+	*Ca+ channel blockers - work mainly on vessels by opening vessels to reduce resistance
-	*ACE inhibitors - reduce cardiac afterload	+	*ACE inhibitors - reduce cardiac afterload (that is, the pressure it takes to eject blood from ventricle)
-	*Diuretics - remove excess water	+	*Diuretics - remove excess water (thus decreasing blood volume / pressure)
	*Digitalis (a drug) - slows HR, conserves energy.		*Digitalis (a drug) - slows HR, conserves energy.
	**Used as a poison in the old days.		**Used as a poison in the old days.
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	*Devices which shock the heart in case of ventricular fibrillation.		*Devices which shock the heart in case of ventricular fibrillation.
	*Used if likely that damaged heart will go into uncontrolled electrical activity.		*Used if likely that damaged heart will go into uncontrolled electrical activity.
-	*Shock the ~~hear tot stTop~~ all electrical activity to it can "reset".	+	*Shock the heart to stop all electrical activity to it can "reset".
	*First used in the 80s.		*First used in the 80s.
-	*Early defibrillators couldn't distinguish between arrhythmia ~~from a~~ rapid heartbeat ~~coming from exercise.~~	+	*Early defibrillators couldn't distinguish between arrhythmia and an exercise-induced rapid heartbeat!
	*Current versions are much smaller.		*Current versions are much smaller.

← Older revision		Revision as of 21:37, 7 March 2010
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	===Electrical activation of the heart===		===Electrical activation of the heart===
-	*The action potentials that are generated at the SA node travel along the conduction system and ~~excited~~ the cardiac muscle fibers.	+	*The action potentials that are generated at the SA node travel along the conduction system and excite the cardiac muscle fibers.
-	*The cardiac ~~aps~~ last hundreds of times longer than a typical nerve action potential.	+	*The cardiac action potentials last hundreds of times longer than a typical nerve action potential.
	*Contractile fibers have resting membrane potentials of about -90mV.		*Contractile fibers have resting membrane potentials of about -90mV.
	*In skeletal muscle, you can get tetanus by stimulating the muscle even at the height of the contraction.		*In skeletal muscle, you can get tetanus by stimulating the muscle even at the height of the contraction.
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	====The specifics of contraction====		====The specifics of contraction====
-	*Three types of channels: sodium, ~~then ..~~.?	+	*Three types of channels: fast sodium, slow chloride, and slow potassium.
	*There is a spike from -90 to +20, then a plateau, then a repolarization.		*There is a spike from -90 to +20, then a plateau, then a repolarization.
	*Sodium is moving into the cells, calcium is moving in, and potassium is moving out.		*Sodium is moving into the cells, calcium is moving in, and potassium is moving out.
	*The sodium channel / movement is extremely rapid.		*The sodium channel / movement is extremely rapid.
-	*The potassium channel closes almost simultaneously with the sodium channel.	+	*The potassium channel closes almost simultaneously with the sodium channel opening.
-	*Long-qt syndrome~~, the~~ first symptom is death. Stimulation of heart is arrested because of a sodium channel gain of function or a potassium channel loss of function.	+	*When channels break:
		+	**Long-qt syndrome can be exhibited.
		+	**The first symptom is death.
		+	**Stimulation of the heart is arrested because of a sodium channel gain of function or a potassium channel loss of function.

	====EKG or ECG====		====EKG or ECG====
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	*There are three waves: P, QRS, and T.		*There are three waves: P, QRS, and T.
	*We're not measuring contractions in the heart, we're measuring electrical activity.		*We're not measuring contractions in the heart, we're measuring electrical activity.
-	*First the SA node fires, the potential is carried across the atria (the P wave), then to the AV node and down the bundle branches (~~some complex wave called~~ the QRS wave), then the potential spreads up the ventricles (the QRS wave), and then ~~relaxation of~~ the ventricles (the T wave).	+	*First the SA node fires, the potential is carried across the atria (the P wave), then to the AV node and down the bundle branches (the QRS wave), then the potential spreads up the ventricles (still the QRS wave), and then the ventricles relax (the T wave).
	*When the P wave is larger (wider) than a standard, then the atrial muscle area is larger than normal.		*When the P wave is larger (wider) than a standard, then the atrial muscle area is larger than normal.
-	**This is likely to be caused by a leaky mitral valve.	+	**This is likely to be caused by a leaky mitral valve (which would cause the hypertrophy of the atrium).
	*An absent P wave can occur when the SA node has failed and the pace makers in the AV node have taken over.		*An absent P wave can occur when the SA node has failed and the pace makers in the AV node have taken over.
	*When the R wave is larger than normal, the ventricles are larger than normal.		*When the R wave is larger than normal, the ventricles are larger than normal.
	**The primary cause of an enlarged R wave is hypertrophy because the ventricles are having to pump harder and are thus growing in size.		**The primary cause of an enlarged R wave is hypertrophy because the ventricles are having to pump harder and are thus growing in size.
-	*A junctional rhythm marks the loss of the SA node. You can tell because the P wave is completely gone and there are fewer heart beats (because the AV node generates fewer beats per minute than the SA node).	+	*A '''junctional rhythm''' marks the loss of the SA node. You can tell because the P wave is completely gone and there are fewer heart beats (because the AV node generates fewer beats per minute than the SA node).
	*A heart block pattern is indicated by P waves not being conducted through the AV node.		*A heart block pattern is indicated by P waves not being conducted through the AV node.
	**This will result in more P waves than QRS complexes.		**This will result in more P waves than QRS complexes.