Limits...
Evaluation of excitation propagation in the rabbit heart: optical mapping and transmural microelectrode recordings.

Mačianskienė R, Martišienė I, Navalinskas A, Vosyliūtė R, Treinys R, Vaidelytė B, Benetis R, Jurevičius J - PLoS ONE (2015)

Bottom Line: Because of the optical features of heart tissue, optical and electrical action potentials are only moderately associated, especially when near-infrared dyes are used in optical mapping (OM) studies.These components correspond to the components of the propagating electrical wave that are transmural and parallel to the epicardium.The co-registration of OM and transmural microelectrode APs enabled the probing depth of fluorescence measurements to be calculated and the OAP upstroke to be divided into two components (depth-weighted and lateral-scattering), and it also allowed the relative strengths of their effects on the shape of the OAP upstroke to be evaluated.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania.

ABSTRACT

Background: Because of the optical features of heart tissue, optical and electrical action potentials are only moderately associated, especially when near-infrared dyes are used in optical mapping (OM) studies.

Objective: By simultaneously recording transmural electrical action potentials (APs) and optical action potentials (OAPs), we aimed to evaluate the contributions of both electrical and optical influences to the shape of the OAP upstroke.

Methods and results: A standard glass microelectrode and OM, using an near-infrared fluorescent dye (di-4-ANBDQBS), were used to simultaneously record transmural APs and OAPs in a Langendorff-perfused rabbit heart during atrial, endocardial, and epicardial pacing. The actual profile of the transmural AP upstroke across the LV wall, together with the OAP upstroke, allowed for calculations of the probing-depth constant (k ~2.1 mm, n = 24) of the fluorescence measurements. In addition, the transmural AP recordings aided the quantitative evaluation of the influences of depth-weighted and lateral-scattering components on the OAP upstroke. These components correspond to the components of the propagating electrical wave that are transmural and parallel to the epicardium. The calculated mean values for the depth-weighted and lateral-scattering components, whose sum comprises the OAP upstroke, were (in ms) 10.18 ± 0.62 and 0.0 ± 0.56 for atrial stimulation, 9.37 ± 1.12 and 3.01 ± 1.30 for endocardial stimulation, and 6.09 ± 0.79 and 8.16 ± 0.98 for epicardial stimulation; (n = 8 for each). For this dye, 90% of the collected fluorescence originated up to 4.83 ± 0.18 mm (n = 24) from the epicardium.

Conclusions: The co-registration of OM and transmural microelectrode APs enabled the probing depth of fluorescence measurements to be calculated and the OAP upstroke to be divided into two components (depth-weighted and lateral-scattering), and it also allowed the relative strengths of their effects on the shape of the OAP upstroke to be evaluated.

No MeSH data available.


Related in: MedlinePlus

Design of the experimental system and data acquisition.(A) Instrumentation for synchronized recording of an OAP and an AP; ME1 and ME2 are the microelectrodes for the subendocardial and epicardial AP recordings. Their locations are indicated by asterisks. A square (dotted line) indicates the field of view of the camera. (B) Intensity changes in the voltage-sensitive signals (ΔF/F, black triangles), the fluorescence level at rest (gray circles) and the time at which dye was injected (gray area). (C) The stimulation protocol with automatic atrial-to-endocardial-to-epicardial pacing switchovers for OAP (normalized upper) and subendo-/epi-AP (in mV lower) recordings.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4400155&req=5

pone.0123050.g001: Design of the experimental system and data acquisition.(A) Instrumentation for synchronized recording of an OAP and an AP; ME1 and ME2 are the microelectrodes for the subendocardial and epicardial AP recordings. Their locations are indicated by asterisks. A square (dotted line) indicates the field of view of the camera. (B) Intensity changes in the voltage-sensitive signals (ΔF/F, black triangles), the fluorescence level at rest (gray circles) and the time at which dye was injected (gray area). (C) The stimulation protocol with automatic atrial-to-endocardial-to-epicardial pacing switchovers for OAP (normalized upper) and subendo-/epi-AP (in mV lower) recordings.

Mentions: Experiments were performed on male New Zealand white rabbits (weight: 3.26 ± 0.27 kg, n = 14). To calm the animals prior to anesthetization, 10 mg/kg xylazine was injected subcutaneously. After 15–20 minutes, the animal was also anesthetized with an intravenous injection of ketamine (10 mg/kg) and heparin (1,000 U/kg) via the marginal ear vein. Then, thoracotomy was performed, and the heart was quickly excised and cannulated through the aorta. Using oxygenated Tyrode’s solution (see the composition below), coronary perfusion was restored within a few minutes using a Langendorff perfusion system with a constant pressure of ~80 mmHg. The coronary flow was 38.3 ± 1.6 mL/min (n = 14). Thereafter, several procedures were performed on the heart (Fig 1A). The following were inserted through a cut in the left atrium into the cavity of the left ventricular (LV) chamber: a bipolar silver electrode for stimulation of the endocardium, an AgCl reference electrode for microelectrode recordings, and a tube for additional perfusion with Tyrode’s solution to prevent the temperature from falling. The excess perfusate allowed the epicardial surface of an air-insulated heart to remain wet. Stimulation was performed from the following locations using the protocol shown in Fig 1C: 1) the right atrium, to evaluate wave propagation from the endocardial to the epicardial (endocardial-to-epicardial) surface (i.e., transmural propagation); 2) the endocardium, to evaluate the propagation both from the endocardial-to-epicardial surface and parallel to the epicardial surface; and 3) the epicardium, to evaluate propagation that is more parallel to the epicardial surface (i.e., lateral propagation). For atrial and epicardial stimulation, bipolar hook electrodes were embedded in the right atrium and the LV epicardial surface, respectively. The heart was continuously paced at 300 ms intervals with a 2 ms pulse width set at twice the diastolic threshold.


Evaluation of excitation propagation in the rabbit heart: optical mapping and transmural microelectrode recordings.

Mačianskienė R, Martišienė I, Navalinskas A, Vosyliūtė R, Treinys R, Vaidelytė B, Benetis R, Jurevičius J - PLoS ONE (2015)

Design of the experimental system and data acquisition.(A) Instrumentation for synchronized recording of an OAP and an AP; ME1 and ME2 are the microelectrodes for the subendocardial and epicardial AP recordings. Their locations are indicated by asterisks. A square (dotted line) indicates the field of view of the camera. (B) Intensity changes in the voltage-sensitive signals (ΔF/F, black triangles), the fluorescence level at rest (gray circles) and the time at which dye was injected (gray area). (C) The stimulation protocol with automatic atrial-to-endocardial-to-epicardial pacing switchovers for OAP (normalized upper) and subendo-/epi-AP (in mV lower) recordings.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400155&req=5

pone.0123050.g001: Design of the experimental system and data acquisition.(A) Instrumentation for synchronized recording of an OAP and an AP; ME1 and ME2 are the microelectrodes for the subendocardial and epicardial AP recordings. Their locations are indicated by asterisks. A square (dotted line) indicates the field of view of the camera. (B) Intensity changes in the voltage-sensitive signals (ΔF/F, black triangles), the fluorescence level at rest (gray circles) and the time at which dye was injected (gray area). (C) The stimulation protocol with automatic atrial-to-endocardial-to-epicardial pacing switchovers for OAP (normalized upper) and subendo-/epi-AP (in mV lower) recordings.
Mentions: Experiments were performed on male New Zealand white rabbits (weight: 3.26 ± 0.27 kg, n = 14). To calm the animals prior to anesthetization, 10 mg/kg xylazine was injected subcutaneously. After 15–20 minutes, the animal was also anesthetized with an intravenous injection of ketamine (10 mg/kg) and heparin (1,000 U/kg) via the marginal ear vein. Then, thoracotomy was performed, and the heart was quickly excised and cannulated through the aorta. Using oxygenated Tyrode’s solution (see the composition below), coronary perfusion was restored within a few minutes using a Langendorff perfusion system with a constant pressure of ~80 mmHg. The coronary flow was 38.3 ± 1.6 mL/min (n = 14). Thereafter, several procedures were performed on the heart (Fig 1A). The following were inserted through a cut in the left atrium into the cavity of the left ventricular (LV) chamber: a bipolar silver electrode for stimulation of the endocardium, an AgCl reference electrode for microelectrode recordings, and a tube for additional perfusion with Tyrode’s solution to prevent the temperature from falling. The excess perfusate allowed the epicardial surface of an air-insulated heart to remain wet. Stimulation was performed from the following locations using the protocol shown in Fig 1C: 1) the right atrium, to evaluate wave propagation from the endocardial to the epicardial (endocardial-to-epicardial) surface (i.e., transmural propagation); 2) the endocardium, to evaluate the propagation both from the endocardial-to-epicardial surface and parallel to the epicardial surface; and 3) the epicardium, to evaluate propagation that is more parallel to the epicardial surface (i.e., lateral propagation). For atrial and epicardial stimulation, bipolar hook electrodes were embedded in the right atrium and the LV epicardial surface, respectively. The heart was continuously paced at 300 ms intervals with a 2 ms pulse width set at twice the diastolic threshold.

Bottom Line: Because of the optical features of heart tissue, optical and electrical action potentials are only moderately associated, especially when near-infrared dyes are used in optical mapping (OM) studies.These components correspond to the components of the propagating electrical wave that are transmural and parallel to the epicardium.The co-registration of OM and transmural microelectrode APs enabled the probing depth of fluorescence measurements to be calculated and the OAP upstroke to be divided into two components (depth-weighted and lateral-scattering), and it also allowed the relative strengths of their effects on the shape of the OAP upstroke to be evaluated.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania.

ABSTRACT

Background: Because of the optical features of heart tissue, optical and electrical action potentials are only moderately associated, especially when near-infrared dyes are used in optical mapping (OM) studies.

Objective: By simultaneously recording transmural electrical action potentials (APs) and optical action potentials (OAPs), we aimed to evaluate the contributions of both electrical and optical influences to the shape of the OAP upstroke.

Methods and results: A standard glass microelectrode and OM, using an near-infrared fluorescent dye (di-4-ANBDQBS), were used to simultaneously record transmural APs and OAPs in a Langendorff-perfused rabbit heart during atrial, endocardial, and epicardial pacing. The actual profile of the transmural AP upstroke across the LV wall, together with the OAP upstroke, allowed for calculations of the probing-depth constant (k ~2.1 mm, n = 24) of the fluorescence measurements. In addition, the transmural AP recordings aided the quantitative evaluation of the influences of depth-weighted and lateral-scattering components on the OAP upstroke. These components correspond to the components of the propagating electrical wave that are transmural and parallel to the epicardium. The calculated mean values for the depth-weighted and lateral-scattering components, whose sum comprises the OAP upstroke, were (in ms) 10.18 ± 0.62 and 0.0 ± 0.56 for atrial stimulation, 9.37 ± 1.12 and 3.01 ± 1.30 for endocardial stimulation, and 6.09 ± 0.79 and 8.16 ± 0.98 for epicardial stimulation; (n = 8 for each). For this dye, 90% of the collected fluorescence originated up to 4.83 ± 0.18 mm (n = 24) from the epicardium.

Conclusions: The co-registration of OM and transmural microelectrode APs enabled the probing depth of fluorescence measurements to be calculated and the OAP upstroke to be divided into two components (depth-weighted and lateral-scattering), and it also allowed the relative strengths of their effects on the shape of the OAP upstroke to be evaluated.

No MeSH data available.


Related in: MedlinePlus