Cardiovascular 20 Flashcards

Question

Draw and label a left ventricular pressure volume loop in a normal adult (40% of marks). List the information that can be obtained from this loop (60% of marks). 2017 march and 2008 march total area of the P-V loop??

Answer 1

Draw and label a left ventricular pressure volume loop in a normal adult (40% of marks). List the information that can be obtained from this loop (60% of marks). 2017 march and 2008 march * Areas: o Total mechanical energy (stroke work), which consists of:  Stroke work, which is the total area of the P-V loop  Stored "potential" mechanical energy (in the LV wall), which is the area under the ESPV

Answer 2

Draw and label a left ventricular pressure volume loop in a normal adult (40% of marks). List the information that can be obtained from this loop (60% of marks). 2017 march and 2008 march * Areas: o Total mechanical energy (stroke work), which consists of:  Stroke work, which is the total area of the P-V loop  Stored "potential" mechanical energy (in the LV wall), which is the area under the ESPV

Answer 3

Draw and label a left ventricular pressure volume loop in a normal adult (40% of marks). List the information that can be obtained from this loop (60% of marks). 2017 march and 2008 march * Areas: o Total mechanical energy (stroke work), which consists of:  Stroke work, which is the total area of the P-V loop  Stored "potential" mechanical energy (in the LV wall), which is the area under the ESPV

Answer 4

Draw and label a left ventricular pressure volume loop in a normal adult (40% of marks). List the information that can be obtained from this loop (60% of marks). 2017 march and 2008 march Examiners comments 2017 Many candidates lost marks for poor quality diagrams with inaccurate labelling. An accurate diagram was required. Many answers lacked sufficient detail regarding contractility and afterload Examiners comments 2008 Candidates were expected to draw and label a diagram showing the relationship between pressure and volume during the different phases of the left ventricular contraction and relaxation (or systole and diastole) Good answers to this question consisted of a well-labelled graph with appropriate scale on both x and y-axes showing all the important events during systole and diastole of the left ventricle. The common omissions were rapid and slow ejection phase during systole, when aortic valve closes, stroke volume, ejection fraction, end-systolic pressure volume line showing the contractility of the left ventricle. Some candidates appeared to have confusion about which line shows contractility and which line shows left ventricular after load. Syllabus C1c Reference: Kam 1 st edition 115-121 Guyton 11 th edition 110 2 candidates (66%) passed this question

Answer 5

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Heart rate preload contractility afterload Cost of electrical conduction basal cost of cardiac metabolism deranged

Answer 6

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Oxygen content of blood Coronary perfusion pressure Anatomy Metabolic activity Autonomic control deranged

Answer 7

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Both ventricles beat at the same rate deranged

Answer 8

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Both ventricles usually have the same preload in the normal heart; deranged

Answer 9

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 left More contractile RightLess contractile deranged

Answer 10

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 left High afterload, and therefore high oxygen demand (more work done to overcome pressure) right Low afterload, less work done to overcome pressure deranged

Answer 11

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Both ventricles have approximately the same content of conductive tissue, and in any case this does not contribute significantly to the overall oxygen demand deranged

Answer 12

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Both ventricles contain the same type of tissue and the basal metabolic rate for myocardiom in general is the same (8ml O2/min/100g, at rest) The left ventricle contains more muscle mass, and the net basal consumption is greater The RV has a lower muscle mass and consumes less total O2 because of this deranged

Answer 13

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Oxygen content of blood . The same aortic blood supplies both ventricles deranged

Answer 14

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Coronary perfusion pressure left High afterload, and therefore high subendocardial systolic pressure (thus, lower blood flow during systole) right Low afterload, low subendocardial systolic pressure, and stable blood flow throughout systole and diastoles deranged

Answer 15

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Coronary perfusion pressure left Anatomy Two major arteries (LAD and LCx) Right One major artery (RCA) deranged

Answer 16

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Metabolic activity Left Owing to oits greater mass, the LV is more metabolically active than the RV Right RV has lower net metabolic activity Both Both ventricles have a high oxygen extraction ratio, and the only way to satisfy increased demand is by increasing blood flow. deranged

Answer 17

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 Autonomic control Coronary arterial vascular resistance is under autonomic control, which is similar for both ventricles deranged

Answer 18

Compare and contrast the supply and demand of oxygen for the right and left ventricle. Appears to be a unique question 2016 aug 7 An integrated answer to supply and demand of oxygen was expected, as a comparison between the right and left ventricles. Many candidates concentrated on differences not similarities. Myocardial oxygen demand was in general poorly described. About 85 - 90% of oxygen demand is for internal work (major determinants wall tension 30 - 40%, heart rate 15 - 25%, myocardial contractility 10 - 15%, basal metabolism 25%). 10 - 15% of oxygen demand for external work or pressure volume work, determined by MPAP x CO. It was expected answers would comment on the phasic nature of coronary blood flow which differs between left and right and the consequence of this to subendocardial oxygen supply during systole usually. Coronary blood flow is affected by coronary perfusion pressure (determined by aortic pressure and RV pressure) & coronary vascular resistance (determined by autoregulation, metabolic factors, humoral factors, nervous control interacting with local endothelial factors) Generally, coronary blood flow is tightly coupled to oxygen demand/consumption due to high basal oxygen consumption (8 - 10 ml/ min/100g) and high oxygen extraction ratio (75%). Better answers noted that oxygen supply can only be increased to cope with increased demand only by increased coronary blood flow. deranged

Answer 19

* Preload can be defined as: o Myocardial sarcomere length just prior to contraction, for which the best approximation is end-diastolic volume o Tension on the myocardial sarcomeres just prior to contraction, for which the best approximation is end-diastolic pressure Define cardiac preload and describe its determinants 2015 aug + 2010 mar

Answer 20

* Preload can be defined as: o Myocardial sarcomere length just prior to contraction, for which the best approximation is end-diastolic volume o Tension on the myocardial sarcomeres just prior to contraction, for which the best approximation is end-diastolic pressure Define cardiac preload and describe its determinants 2015 aug + 2010 mar

Answer 21

* The determinants of preload, if we choose to define it as a volume, are: . o Pressure filling the ventricle:  Intrathoracic pressure (high pressure decreases preload)  Atrial pressure  Atrial contractility and rhythm (SR increases preload, AF decreases preload)  Atrioventricular valve competence (mitral and tricuspid stenosis decrease preload)  Ventricular end-systolic volume (increased end-systolic volume increases preload by adding to venous return)  Ventricular compliance (decreased compliance decreases preload)  Right atrial pressure (high right atrial pressure increases preload)  Mean systemic filling pressure  Total venous blood volume (increased volume increases preload)  Venous vascular compliance (decreased compliance, i.e. venoconstriction, increases preload)  Cardiac output, insofar as it supplies the total blood volume / o Compliance of the ventricle:  Pericardial compliance:  Compliance of the pericardial walls (decreased compliance decreases preload)  Compliance of the pericardial contents (increased contents volume decreases preload)  Ventricular wall compliance:  Duration of ventricular diastole (a longer diastole increases preload)  Wall thickness (a thicker wall decreases preload)  Relaxation (lusitropic) properties of the muscle (poor relaxation decreases preload)  End-systolic volume of the ventricle (i.e. afterload) - increased end-systolic volume decreases preload Define cardiac preload and describe its determinants 2015 aug + 2010 mar

Answer 22

2015 aug Q15 This question required synthesis and application of knowledge derived from multiple sources rather than regurgitation of a published list in a text. Many candidates failed to recognise that venous return is not the only determinant of preload. Most candidates failed to discuss determinants of venous return. Factors such as contractility, afterload or chamber filling and emptying can all impact preload. In addition to listing determinants the question required an explanation of their relationship with preload (e.g. the direction of change). A discussion about the determinants of cardiac output was not asked for as did not score marks. "better answers included discussion of the effects of afterload, arrhythmias, and valvular pathology. A distinction between the factors determining left and right ventricular preload would have demonstrated a more sophisticated understanding of the physiology" 2010 march Q21 A definition based on stretch of the isolated myocyte prior to contraction, and extrapolation to the human heart, was expected. Surrogate measures of preload used in clinical practice needed to be explained and related to the definition (for example, end-diastolic volume and central venous pressure). The Frank-Starling Law was relevant to discussion of the significance of preload to cardiac performance. A diagram illustrating the interaction of important factors would have been helpful in answering this question. At a minimum, detail should have included atrial contractility, diastolic filling time, ventricular compliance, and the determinants of venous return. Better answers included discussion of the effects of afterload, arrhythmias, and valvular pathology. A distinction between the factors determining left and right ventricular preload would have demonstrated a more sophisticated understanding of the physiology Define cardiac preload and describe its determinants 2015 aug + 2010 mar

Answer 23

Summary of examiners comments over 3 questions (cardio resp, all and all) Include; lung volume, dead space, arterial pO2 and intrapleural pressure. Include effect on cardiac output, blood pressure and oxygen delivery. The physiological impact of lower levels PEEP in a young healthy person is different to that often seen in the critically ill and this was not appreciated by most candidates. ---- A definition of PEEP is a useful way to start this answer and this was missing in more than half the answers. Many candidates incorrectly concluded that PEEP would increase afterload and decrease pulmonary vascular resistance. Some candidates provided description of the cardiovascular effects of Valsalva, which was not part of the question. It was expected candidates would also mention physiological effects on other organ systems such as potential cerebral and renal effects. Points required included a definition of PEEP, both intrinsic and extrinsic Respiratory including increased FRC, increased compliance and decreased work of breathing. Cardiovascular consequences include decreased venous return and subsequently decreased cardiac output and an increased pulmonary vascular resistance. Renal consequences include decreased renal blood flow and increased ADH Effects on intra-abdominal pressure, hepatic blood flow and the beneficial effects in cardiac failure earned marks.

Answer 24

Respiratory effects of positive pressure ventilation: * PEEP increases functional residual capacity (FRC) * By increasing FRC, PEEP: o Increases alveolar recruitment, which gives rise to:  Improved V/Q matching  Increased total gas exchange surface o Increases lung compliance o Decreases the work of breathing (done against compliance) * Positive pressure may also redistribute lung water out of the lung interstitium * Excessive positive pressure leads to o Overdistension and lung injury o Worsening V/Q matching o "Biotrauma", i.e. cytokine leak and extrapulmonary organ dysfunction deranged 2016 and 2014

Answer 25

Cardiovascular effects of positive pressure ventilation: * Effects on the right ventricle and the pulmonary circulation: o Increased intrathoracic pressure is transmitted to central veins and the right atrium, decreasing right ventricular preload o Increased intrathoracic pressure is transmitted to pulmonary arteries o Transmitted alveolar pressure increases pulmonary vascular resistance o Increased pulmonary vascular resistance increases right ventricular afterload o Thus, increased afterload and decreased preload has the net effect of decreasing the right ventricular stroke volume. * Effects on the left ventricle and the systemic circulation: o Decreased preload by virtue of lower pulmonary venous pressure o Decreased afterload due to a reduction in LV end-systolic transmural pressure and an increased pressure gradient between the intrathoracic aorta and the extrathoracic systemic circuit o Thus, decreased LV stroke volume * Effects on overall cardiovascular function: o Decreased cardiac output o Decreased myocardial oxygen consumption deranged 2016 and 2014

Answer 26

Other organ system effects of positive pressure ventilation: * Raised intracranial pressure, if the PEEP is very high * Water retention due to increased ADH release and aldosterone secretion * Sodium retention due to decreased ANP release and aldosterone secretion * Decreased renal perfusion and GFR (due to decreased cardiac output and increased renal venous pressure) * Decreased hepatic perfusion and thus decreased metabolic clearance of drugs * Decreased splanchnic perfusion, resulting id decreased intestinal motility and poor gastric emptying * Decreased gastric perfusion, increasing the risk of stress ulceration * Neutrophil retention in the pulmonary capillaries * Impaired lymphatic drainage from the lungs deranged 2016 and 2014

Answer 27

2016 march: Describe the Respiratory and cardiovascular effects of applying 10 cm of PEEP (positive end-expiratory pressure) to a healthy mechanically ventilated adult. I think this is essentially a repeat of 2014 august, but 2016 has a completely different answer, need to make one good answer, 2009 feb This topic has been asked previously. It was expected candidates could detail the impact of PEEP on a variety of respiratory parameters such as lung volume, dead space, arterial pO2 and intrapleural pressure. The cardiovascular consequences are well described including the effect on cardiac output, blood pressure and oxygen delivery. The physiological impact of lower levels PEEP in a young healthy person is different to that often seen in the critically ill and this was not appreciated by most candidates. 2014 AUG-3 Describe the physiological consequences of Positive End-Expiratory Pressure (PEEP) I think this is essentially a repeat of 2014 august, but 2016 has a completely different answer, need to make one good answer, 2009 feb Most answers were quite brief and superficial. They simply did not cover enough of the required knowledge base to gain a pass mark. A definition of PEEP is a useful way to start this answer and this was missing in more than half the answers. Deficiencies in knowledge included even the primary respiratory and cardiovascular effects of PEEP. Many candidates incorrectly concluded that PEEP would increase afterload and decrease pulmonary vascular resistance. Some candidates provided description of the cardiovascular effects of Valsalva, which was not part of the question. It was expected candidates would also mention physiological effects on other organ systems such as potential cerebral and renal effects. This topic (Level 1) requires a detailed knowledge and candidates should read widely to gain the depth of understanding required. The core material is covered in texts such as Nunn’s’ Applied Respiratory Physiology and additional applied information can be found in a variety of texts such as Textbook of Critical Care by Fink et al, Irwin and Rippe’s Intensive Care Medicine or Miller’s Anaesthesi 2009 march 17 Describe the physiological consequences of positive end expiratory pressure. I think this is essentially a repeat of 2014 august, but 2016 has a completely different answer, need to make one good answer, 2009 feb Points required included a definition of PEEP, both intrinsic and extrinsic. The important physiological consequences that need to be discussed are respiratory including increased FRC, increased compliance and decreased work of breathing. Cardiovascular consequences include decreased venous return and subsequently decreased cardiac output and an increased pulmonary vascular resistance. Renal consequences include decreased renal blood flow and increased ADH Effects on intra-abdominal pressure, hepatic blood flow and the beneficial effects in cardiac failure earned marks.

Answer 28

2009 march 17 Describe the physiological consequences of positive end expiratory pressure. I think this is essentially a repeat of 2014 august, but 2016 has a completely different answer, need to make one good answer, 2009 feb Deranged Discussion The question did not specifically ask for a definition, let alone a definition of intrinsic PEEP, and so the trainees would have been quite surprised to find this among the essential points expected of a passing answer. In spite of these hidden gems, 40% seem to have passed. Deranged specific answer 392 words below Definitions: PEEP (positive end-expiratory pressure) is "a residual pressure above atmospheric maintained at the airway opening at the end of expiration” (Joint Committee on Pulmonary Nomenclature of the American Thoracic Society and the American College of Chest Physicians, 1975) Intrinsic PEEP has no official definition, but one example of a good description is from Brander & Slutsky (2012): "when expiratory flow has not emptied alveoli to their resting FRC values by the end of exhalation... [intrinsic PEEP is] the residual positive pressure within the lungs referenced to atmospheric pressure or to PEEP"

Cardiovascular 20 Flashcards

(52 cards)