Transcript An Investigation of Cardiac Dynamics and Substrate

An Investigation of Cardiac
Dynamics and Substrate
Metabolism in an Animal Heart
Failure Model
Anna E. Stanhewicz
Heart Failure
• Heart disease is the primary cause of death in the US
• Heart Failure: insufficient blood supply to the body
• Progressive disease
Early Stage Risk Factors
Heart Attack, Hypertension
May go unnoticed
Compensated Phase
Cardiac output is maintained
Patient does not experience symptoms
Decompensated End Stage
Significant decline in cardiac output
Patient experiences symptoms
Death
How the Heart Works
Systole – contraction
Diastole - relaxation
Right Atrium
Left Atrium
Left Ventricle
Right Ventricle
Heart Failure is Characterized
by a Combination of Dynamic
and Metabolic Changes
Dynamic Changes
Decreased Cardiac Output and Ejection Fraction
Key element is cardiac hypertrophy
Response to increased vascular resistance
Changing size and shape
• Diastolic dysfunction
• Systolic dysfunction
Diastolic
Systolic
dysfunction dysfunction
Cardiac
Output
Ejection
Fraction
unchanged
Thick Walls Weak Heart
Healthy Heart
Compensated
Heart Failure
Metabolic Changes
Healthy heart: 60-90% fatty acids
10-40% carbohydrate (glucose)
In HF we see a change in substrate preference
from fatty acids to carbohydrate
% Substrate Utilization
Expected Metabolic Profile as HF Progresses
100
Fatty Acid
Carbohydrate
0
Time
Project Goals:
1. Develop working knowledge of the
perfused mouse heart system
2. Use perfused mouse heart to measure
cardiac dynamics and substrate
metabolism simultaneously
Methods
Perfused Working Mouse Heart
• Allows for measurement of myocardial function and
metabolism under defined loading conditions
• Ex Vivo - Independent of neurohormonal influence
• Desirable
– easy genetic modification, rapid reproductive cycle, similarity to
human physiology
Methods
Perfused Working Mouse Heart
First perfused through the aorta (retrograde) with KrebsHenseleit solution
Then perfused through the left ventricle (anterograde) with
physiologic buffers
Temperature, filling pressure and resistance to aortic
outflow maintained at physiologic levels
Methods
Dynamic Measurements
1.4F Millar Mikro-Tip® Ultra-miniature P-V Catheter
Inserted through the apex of the heart into the left ventricle
Measures changing pressures and volumes
Data integrated into PVAN software
Methods
Metabolism- Measurement of 3H2O production
from radio labeled substrate
• Glycolysis
– 5-[3H]glucose → [3H2O]
• Fatty Acid Oxidation
– 9,10-[3H]palmitate → [3H2O]
• 0.2mL of perfusate taken every 10 min
• 0.18mL of each sample run through Dowex
chromatography column – counted for 3H2O
activity
Measures of Dynamic Function
Left Ventricular Pressure (mmHg)
Pressure Waves in Working Mouse Heart
Time (sec)
HR=300bpm unpaced
Dynamic Results Obtained from
PVAN Software
340
Stroke Volume (μL)
19.79
Ejection fraction (%)
11.41
Cardiac output (mL/min)
6.68
End-systolic pressure
(mmHg)
61.28
End-systolic volume (μL)
160.41
End-diastolic pressure
(mmHg)
End-diastolic volume (μL)
11.84
171.75
Pressure-Volume Loops in Working Mouse
Heart
Left Ventricular Pressure (mmHg)
Heart Rate (bpm)
70
60
50
40
30
20
10
0
0
10
20
30
40
50
Left Ventricular Volume (μL)
60
Metabolism Results
Glycolysis
Rate = 4.97 μmoles·g-1dry weight·min-1
Glucose Metabolism in Working Mouse Heart
μmole •g dry weight-1
350
y = 4.97x
R2 = 0.97
300
250
200
150
100
50
0
0
10
20
30
40
Time (min)
50
60
70
Metabolism Results
Fatty Acid Oxidation
Rate = 0.80 μmoles· g dry weight-1·min-1
μmole •g dry weight-1
Fatty Acid Metabolism in Working Mouse Heart
30
y = 0.80x + 0.04
R2 = 0.97
25
20
15
10
5
0
0
5
10
15
20
Tim e (m in)
25
30
35
Discussion
• With this system dynamic and metabolic measures were
obtained simultaneously
• This holds great potential for drug development studies
• Lays groundwork for more developed understanding of
complexities of heart failure
Early detection
Intervention
Acknowledgements
Thomas Manfredi, Ph.D.
Robert Rodgers, Ph.D.
Fredrick Vetter, Ph.D.
Arthur Cosmos, Ph.D.
Michael Dunn, Ph.D. Candidate