What question did this study set out to answer?

To analyze whether acute transmural myocardial ischemia alters the normal systolic-diastolic phasic pattern of myocardial electrical resistivity across the cardiac cycle.

November 26, 2015AJP Heart and Circulatory PhysiologyOpen Access

Early detection of acute transmural myocardial ischemia by the phasic systolic-diastolic changes of local tissue electrical impedance

Q: What are the key findings of this study?

Acute coronary occlusion in a pig model reduced the area under the left ventricular pressure-impedance curve from 1427 to 757 Ω·cm·mmHg and progressively increased mean myocardial resistivity.

Q: What is the clinical evidence from this study?

Study design: Other. Population: Acute myocardial ischemia (n=7). Intervention: Acute left anterior descending coronary artery occlusion vs. Baseline (pre-occlusion). Primary outcome: Area under the LV pressure-impedance curve at 41 kHz (p=<0.01).

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Key result

Acute coronary occlusion in pigs reduces LV pressure-impedance area ~47% and progressively increases myocardial resistivity.

P<0.01
n=7

Why the study?

Does acute coronary occlusion alter the phasic systolic-diastolic changes of local tissue electrical impedance in an open-chest pig model?

Population

7 anesthetized open-chest pigs

Comparison

30 min regional ischemia by acute left anterior… vs Baseline (normal conditions)

Design

Preclinical

Follow-up

30 min

Authors

EJEsther JorgeUniversitat de Vic - Universitat Central de Catalunya GAGerard Amorós-FiguerasHospital de Sant Pau TGTomás García-SánchezUniversitat Pompeu Fabra

Discussion

Member takes

Implication

Hypothesis-generating for impedance-based ischemia detection; leaves open translation to clinical use.

Key Points

To analyze whether acute transmural myocardial ischemia alters the normal systolic-diastolic phasic pattern of myocardial electrical resistivity across the cardiac cycle.
Studied 7 anesthetized open-chest pigs subjected to 30 minutes of regional myocardial ischemia via acute occlusion of the left anterior descending coronary artery.
Continuously recorded myocardial resistivity across the cardiac cycle at 26 simultaneous excitation frequencies (1 kHz to 1 MHz) alongside electrocardiogram, left ventricular (LV) pressure, LV dP/dt, and aortic blood flow.
Baseline myocardial resistivity demonstrated a phasic cycle, peaking at the preejection period (+4.19 ± 1.09% above the mean, P < 0.001) and reaching its nadir during relaxation (-5.01 ± 0.85% below the mean, P < 0.001).
Acute coronary occlusion caused an early holosystolic resistivity rise within 5 minutes, forming a bell-shaped waveform and decreasing the area under the LV pressure-impedance curve from 1,427 ± 335 to 757 ± 266 Ω·cm·mmHg (P < 0.01 at 41 kHz).
Ischemia induced a progressive rise in mean resistivity between 5 and 10 minutes, increasing from 325 ± 23 to 438 ± 37 Ω·cm by 30 minutes of occlusion (P < 0.01 at 1 kHz).

Structured PICO

Does acute coronary occlusion alter the phasic systolic-diastolic changes of local tissue electrical impedance in an open-chest pig model?

Population

7 anesthetized open-chest pigs

Intervention

30 min regional ischemia by acute left anterior descending coronary artery occlusion

Comparator

Baseline (normal conditions)

Outcome

Phasic changes of myocardial resistivity measured continuously during the cardiac cycle using 26 different simultaneous excitation frequencies (1 kHz-1 MHz)surrogate

Main Result

Absolute Event Rate: 757% vs 1427%

p-value: p=<0.01

Specific changes in the systolic-diastolic myocardial resistivity curve can detect structural and mechanical myocardial dysfunction induced by acute coronary occlusion, suggesting its potential as a surrogate indicator of evolving acute myocardial ischemia.

Limitations

Invasive approach requiring a thoracotomy
Use of intramural needle electrodes in an open chest swine model

Cite This Study

Jorge et al. (2015) studied Acute myocardial ischemia (n=7). Acute left anterior descending coronary artery occlusion vs. Baseline (pre-occlusion) was evaluated on Area under the LV pressure-impedance curve at 41 kHz (p=<0.01). Acute coronary occlusion in a pig model reduced the area under the left ventricular pressure-impedance curve from 1427 to 757 Ω·cm·mmHg and progressively increased mean myocardial resistivity.

synapsesocial.com/papers/6a0d6e9ecae7912d2fa4ffe2 https://doi.org/10.1152/ajpheart.00754.2015

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Early detection of acute transmural myocardial ischemia by the phasic systolic-diastolic changes of local tissue electrical impedance

Discussion

Member takes

Implication

Key Points

Structured PICO

Main Result

Limitations

Cite This Study

Early detection of acute transmural myocardial ischemia by the phasic systolic-diastolic changes of local tissue electrical impedance

Discussion

Member takes

Implication

Key Points

Structured PICO

Main Result

Limitations

Cite This Study

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