What is ventricle fibrillation (Vfib)? | Circulatory System and Disease | NCLEX-RN | Khan Academy — Transcript

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1. 0:01- [Voiceover] Let's talk about ventricular fibrillation,
2. 0:03also known as V-fib.
3. 0:06This is an abnormal, deadly heart rhythm,
4. 0:09where the ventricles, which I'm outlining right here,
5. 0:12these lower chambers of the heart,
6. 0:13the ventricles lose the ability to contract
7. 0:16and circulate blood to the rest of the body,
8. 0:20and that's why V-fib is so deadly.
9. 0:23So, over here we have a heart diagram,
10. 0:25looking at the inside of the heart,
11. 0:26just like we did on the left,
12. 0:28but this diagram on the right highlights
13. 0:30some of the important structures
14. 0:32in the electrical conduction system.
15. 0:35And I've taken out the big vessels,
16. 0:37so that way you can get a better view
17. 0:38of the inside of the heart.
18. 0:40So, in a normal heart, the electrical conduction
19. 0:42starts at the sinoatrial node, also known as the SA node.
20. 0:48So, sinoatrial, SA node.
21. 0:53The signal travels from the SA node
22. 0:55down to another structured called
23. 0:58the atrioventricular or AV node.
24. 1:03So, that stands for atrioventricular or AV node.
25. 1:11From the AV node, the signal goes down to the ventricles
26. 1:15and signals to the ventricles
27. 1:16and makes the ventricular cells and the walls contract.
28. 1:21When these walls contract, that's when blood
29. 1:22is pushed out to the rest of the body.
30. 1:25Now in V-fib, the signal in the ventricles
31. 1:27is no longer coordinated.
32. 1:29This might be because you have some sort of
33. 1:32severe oxygen deprivation or because you have
34. 1:35some sort of abnormality in conduction,
35. 1:37but for whatever reason,
36. 1:38you lose coordinated signaling in the ventricles.
37. 1:41Instead, you have this rapid, random, and chaotic signaling.
38. 1:46This chaotic signaling leads to
39. 1:48the ventricular walls spasming,
40. 1:52and when the ventricular walls spasm,
41. 1:54blood can't be circulated through the body.
42. 1:57It just stays here in the heart.
43. 1:59If you're not circulating blood to the rest of the body,
44. 2:01you're depriving all of the other organs of oxygen.
45. 2:05Another way to think about this is,
46. 2:07think about if you were squeezing a tube of toothpaste.
47. 2:11So, here you have a hand squeezing a tube of toothpaste,
48. 2:14and you can imagine that if you squeeze
49. 2:17with all your fingers at the same time,
50. 2:20you're going to get the most toothpaste out.
51. 2:24So, if you coordinate all your fingers
52. 2:26to squeeze at the same time,
53. 2:27you're going to squeeze out the most toothpaste,
54. 2:29as opposed to if you squeezed your pinky
55. 2:32and then your index finger and then your thumb,
56. 2:35you're not going to squeeze out a bunch of toothpaste.
57. 2:37This is the same idea as ventricular fibrillation.
58. 2:39You lose this coordinated contraction
59. 2:41and this coordinated squeeze
60. 2:42to distribute blood to the rest of the body,
61. 2:44and instead you have random firing of muscle cells,
62. 2:46leading to this spasm,
63. 2:48and you're not going to push out a lot of toothpaste
64. 2:51or blood to the rest of the body.
65. 2:53If V-fib isn't reversed immediately through electric shock,
66. 2:56you're going to have permanent brain damage and death,
67. 3:02because the brain and the body
68. 3:03aren't getting enough oxygen.
69. 3:05A person whose heart is in V-fib
70. 3:08is not going to be conscious,
71. 3:09since they have no blood circulating,
72. 3:12and you won't be able to feel a pulse.
73. 3:14Pulses are made by forward movement
74. 3:17of blood to the vessels, so if you have no
75. 3:19forward movement of blood to the vessels,
76. 3:20you're not going to have a pulse.
77. 3:22Sometimes, right before someone collapses
78. 3:24from ventricular fibrillation,
79. 3:25they might complain of signs or symptoms of a heart attack,
80. 3:29like chest pain or numbness or tingling in their left arm,
81. 3:33and that's because the heart is getting deprived of oxygen.
82. 3:37Since the heart's not circulating blood
83. 3:39to the rest of the body,
84. 3:40it can't circulate blood to the heart itself,
85. 3:43and since skin isn't getting oxygenated blood,
86. 3:45you might see the skin turn pale or even a blue color.
87. 3:51This is also known as cyanosis.
88. 3:53That's the blue-color skin when you're not
89. 3:55circulating oxygen through the body.
90. 3:58An EKG in someone in V-fib looks like this.
91. 4:01You're going to see course squiggly lines.
92. 4:04This is because you lose this smooth signaling
93. 4:07from the SA node to the AV node to the ventricles.
94. 4:10Instead, in the ventricles you have this
95. 4:12chaotic, erratic signaling,
96. 4:14which looks like course squiggly lines on EKG.
97. 4:17The ventricles are just spasming.
98. 4:21Now, what are the big risk factors of V-fib?
99. 4:24Well, I like to separate
100. 4:25the major risk factors into two categories.
101. 4:27The first one being anything that causes
102. 4:30general irritability to the ventricular cells.
103. 4:33Now, an irritable ventricular cell means
104. 4:35that it's likely to just over-fire or fire abnormally.
105. 4:42The other risk factors for V-fib is
106. 4:44anything that causes scar tissue formation.
107. 4:49Now, let's go back to the irritable ventricular cells.
108. 4:51What would cause ventricular cells to be irritated?
109. 4:54Well, the most classic example is coronary artery disease.
110. 4:59Coronary arteries are the blood vessels
111. 5:01that supply the heart with oxygenated blood,
112. 5:04and over time these blood vessels can get clogged,
113. 5:07and this might be because of years of smoking
114. 5:09or bad diet, but over time these vessels get clogged.
115. 5:14When the coronary arteries are clogged,
116. 5:16you've got less blood flow to the ventricular cells.
117. 5:19These cells get less oxygen than they're used to having,
118. 5:22so they become irritated,
119. 5:24and they're more likely to over-fire or fire abnormally.
120. 5:28Also, certain electrolyte abnormalities,
121. 5:31like high potassium or low calcium or low magnesium
122. 5:36might cause ventricular cells to become irritable.
123. 5:39And why is that?
124. 5:41Well, electrolytes play an important role
125. 5:43of normal electric conduction in the heart.
126. 5:45And you can imagine if the electrolytes
127. 5:47don't have the right levels,
128. 5:49this could disrupt normal electric conduction
129. 5:51through the heart.
130. 5:53Okay, and now for scar tissue.
131. 5:55So, we said scar tissue can also set up the heart
132. 5:58for ventricular fibrillation.
133. 5:59So, what might cause scar tissue?
134. 6:01Well, the most classic example is a heart attack.
135. 6:06Like we said, we have coronary arteries
136. 6:08that supply the heart with oxygenated blood.
137. 6:12When you have a heart attack,
138. 6:14there is a coronary artery that gets clogged, totally,
139. 6:18so no blood is getting to this part of the heart.
140. 6:22So, whereas in coronary artery disease
141. 6:25you had less blood flow,
142. 6:27in heart attack you have no blood flow
143. 6:30to this part of the heart, and this tissue ends up dying,
144. 6:35and it's replaced by protein, kind of like a scab,
145. 6:39and it creates this scar tissue.
146. 6:41Now, scar tissue doesn't function like regular heart tissue.
147. 6:45It's not going to conduct signal
148. 6:48like regular heart tissue would.
149. 6:49Instead, it sets up for abnormal firing
150. 6:52or abnormal circuits in the heart.
151. 6:55And this disruption in electrical conduction
152. 6:57can set up the heart for ventricular fibrillation.
153. 7:00Other things that can lead to scar tissue formation
154. 7:03is a cardiomyopathy.
155. 7:07So, cardiomyopathy just means disease of heart tissue,
156. 7:10in which the heart tissue doesn't function as well.
157. 7:14So, it loses function.
158. 7:17It doesn't lose all function,
159. 7:19but it doesn't function as well as a normal heart would.
160. 7:22Cardiomyopathies have a lot of causes.
161. 7:24So, infection can be a cause.
162. 7:26So, there are some viruses that affect the heart
163. 7:29and make the heart tissue actually decrease function.
164. 7:33There are certain genetic disorders
165. 7:36that can cause a cardiomyopathy,
166. 7:40and these disorders will actually change the structure
167. 7:43of the tissue of the heart, making them lose function,
168. 7:47and also years of coronary artery disease,
169. 7:49which I'm going to write as CAD,
170. 7:52so, years of coronary artery disease,
171. 7:54where the heart is constantly getting less oxygen
172. 7:57than it optimally wants over years.
173. 7:59Eventually, that heart tissue is going to lose function.
174. 8:03Again, all of these things from the cardiomyopathies
175. 8:05predispose the heart to have scar formation,
176. 8:08and scar disrupts normal electrical conduction
177. 8:12and can set the heart up for V-fib.
178. 8:14And one final thing that might cause ventricular fibrillation
179. 8:17that's not as common is electrocution.
180. 8:22In electrocution, you have some sort of
181. 8:24outside source of electricity entering the body.
182. 8:27So, where the heart would have a normal
183. 8:28electrical conduction system,
184. 8:30electrocution is going to disrupt this normal signaling,
185. 8:37and that can lead to ventricular fibrillation.