scholarly journals Anatomy of the Heart with the Highest Heart Rate

2021 ◽  
Author(s):  
Yun Hee Chang ◽  
Boris I Sheftel ◽  
Bjarke Jensen
Keyword(s):  
Heart Rate ◽  
Coronary Arteries ◽  
Developmental Process ◽  
Sinus Node ◽  
Relative Size ◽  
Coronary Vessels ◽  
Micro Computed Tomography ◽  
Segmental Analysis ◽  
Luminal Side ◽  
The Right

Shrews occupy the lower extreme of the seven orders of magnitude mammals range in size. Their hearts are large relative to body weight and heart rate can exceed a thousand beats a minute. To investigate whether cardiac traits that are typical mammalian scale to these extremes, we assessed the heart of three species of shrew (genus Sorex) following the sequential segmental analysis developed for human hearts. Using micro-computed tomography we describe the overall structure and find, in agreement with previous studies, a large and elongate ventricle. The atrial and ventricular septums and the atrioventricular and arterial valves are typically mammalian. The ventricular walls comprise mostly compact myocardium and especially the right ventricle has few trabeculations on the luminal side. A developmental process of compaction is thought to reduce trabeculations in mammals, but in embryonic shrews the volume of trabeculations increase for every gestational stage, only slower than the compact volume. By expression of Hcn4, we identify a sinus node and an atrioventricular conduction axis which is continuous with the ventricular septal crest. Outstanding traits include pulmonary venous sleeve myocardium that reaches farther into the lungs than in any other mammals. Typical proportions of coronary arteries-to-aorta do not scale and the shrew coronary arteries are proportionally enormous, presumably to avoid the high resistance to blood flow of narrow vessels. In conclusion, most cardiac traits do scale to the miniscule shrews. The shrew heart, nevertheless, stands out by its relative size, elongation, proportionally large coronary vessels, and extent of pulmonary venous myocardium.

Long-term effects of hyperpolarization-activated inward current blockade on cardiac parasympathetic activity

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
A Scridon ◽  
VB Halatiu ◽  
AI Balan ◽  
DA Cozac ◽  
GV Moldovan ◽  
...  
Keyword(s):  
Heart Rate ◽  
Vagus Nerve ◽  
Vagal Stimulation ◽  
Sinus Node ◽  
Vagal Tone ◽  
Right Atrial ◽  
The Right

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI Background The autonomic control of the pacemaker current, If, and the molecular mechanisms underlying parasympathetic If modulation are well understood. Conversely, the effects of chronic If blockade on the parasympathetic nervous system and on the heart rate (HR) response to acute parasympathetic changes are still largely unknown. Such interactions could significantly influence the course of patients undergoing chronic therapy with the If blocker ivabradine. Purpose We aimed to assess the effects of long-term If blockade using ivabradine on cardiac autonomic modulation and on the cardiovascular response to acute in vivo and in vitro parasympathetic stimulation. Methods Radiotelemetry ECG transmitters were implanted in 6 Control and 10 ivabradine-treated male Wistar rats (IVA; 3 weeks, 10 mg/kg/day); sympathetic and parasympathetic heart rate variability parameters were assessed. At the end of the study, the right atrium was removed and right atrial HCN(1-4) RNA expression levels were analyzed. The HR and systolic blood pressure (SBP) responses to in vivo electrical stimulation of the right vagus nerve (2–20 Hz) and the spontaneous sinus node discharge rate (SNDR) response to in vitro cholinergic receptors stimulation using carbamylcholine (10-9–10-6 mol/L) were assessed in 6 additional Control and 10 IVA rats. Results At the end of the study, mean 24-h HR was significantly lower in the IVA compared with the Control rats (301.3 ± 7.5 bpm vs. 341.5 ± 8.3 bpm; p< 0.01). Ivabradine administration led to a significant increase in vagal tone and shifted the sympatho-vagal balance towards vagal dominance (awake, asleep, and over 24-h; all p< 0.05). In the Control rats, in vivo vagus nerve stimulation induced a progressive decrease in both the SBP (p = 0.0001) and the HR (p< 0.0001). Meanwhile, in the IVA rats, vagal stimulation had no effect on the HR (p = 0.16) and induced a significantly lower drop in SBP (p< 0.05). Ivabradine-treated rats also presented a significantly lower SNDR drop in response to carbamylcholine (p< 0.01) and significantly higher HCN4 expression (p = 0.02). Conclusion Long-term If blockade using ivabradine caused a significant increase in vagal tone and shifted the autonomic balance towards vagal dominance in rats. Given the highly proarrhythmic effects of vagal activation at the atrial level, these findings could provide an explanation for the increased risk of atrial fibrillation associated with ivabradine use in clinical trials. In addition, ivabradine reduced the HR response to direct muscarinic receptors stimulation, canceled the cardioinhibitory response and blunted the hemodynamic response to in vivo vagal stimulation, and led to significant sinus node HCN4 up-regulation. These data suggest that ivabradine-induced HCN4 and the consequent If up-regulation could render the sinus node less sensitive to acute vagal inputs and could thus protect against excessive bradycardia induced by acute vagal activation.

A CADAVERIC STUDY ON CORONARY ARTERY VARIATIONS AND ITS CLINICAL `SIGNIFICANCE

2021 ◽  
pp. 20-22
Author(s):  
Sony Jhansi Priya ◽  
Sangeetha A ◽  
M. Sai Krishna
Keyword(s):  
Coronary Artery ◽  
Coronary Arteries ◽  
Left Coronary Artery ◽  
Coronary Vessels ◽  
Average Diameter ◽  
Cadaveric Study ◽  
Aortic Sinus ◽  
Clinical Procedures ◽  
Human Cadavers ◽  
The Right

Coronary artery variations are one of the commonest variations observed during clinical procedures. Normally, there are two main coronary arteries, the right coronary artery (RCA), left coronary artery (LCA).Left coronary artery gives two important branches left circumex artery (LCX) and left anterior descending (LAD) arteries. Knowledge about the coronary vessels and its variations are essential to clinicians to prevent untoward injury of vessels during any procedures. To study the morphology and variations of coronar Aim: y arteries by dissection. Materials and Methods: The present study was a cadaveric study which was conducted on 50 hearts obtained from adult human cadavers. Coronary arteries were dissected to see the origin, course and variations. The data was entered in Microsoft excel sheet and expressed in percentage. The Right Results: coronary artery branched out from the right aortic sinus and had an average diameter of 3.5mm. The left coronary artery arouse from left aortic sinus and had an average diameter of 4mm. LMCA divided into two branches in 60 percent, three branches in 30 percent and four branches in 06 percent of the hearts and direct branches from left aortic sinuus in 4 percent hearts.Based on the origin of Posterior descending or interventricular artery, Right dominance was observed in 68 percent, left dominance in 26 percent, and equal dominance in 06 percent of the hearts. Conclusion: Knowledge about the variations of coronary vessels is a prerequisite for clinicians to perform interventions of coronary vessels.

P1096Cardioneuroablation changes the type of vaso-vagal response in patients with asystolic reflex syncope

EP Europace ◽  
2020 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
R Piotrowski ◽  
A Zuk ◽  
J Baran ◽  
A Sikorska ◽  
T Krynski ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Postgraduate Medical Education ◽  
Sinus Node ◽  
Pacemaker Implantation ◽  
Heart Rate Variability Parameter ◽  
History Of ◽  
The Right ◽  
The Impact

Abstract Funding Acknowledgements Centre of Postgraduate Medical Education No. 501-1-10-14-19 Background. Cardioneuroablation (CNA) - ablation of ganglionated plexi (GP) to eliminate or reduce parasympathetic overactivity, has been recently proposed as a new therapeutic method in patients with vaso-vagal syncope (VVS) due to cardioinhibitory or mixed mechanism. Purpose. To assess the impact of CNA on the type of VV response during tilt testing (TT). Methods. The study group consisted of the first 20 patients (7 males, mean age 38 ± 9 – year – old) enrolled in the ongoing prospective Roman study (NCT 03903744). All patients had a history of ECG documented syncope due to asystole and confirmed asystolic form of VVS at baseline TT. CNA was performed using electroanatomical system Carto 3 and radiofrequency applications delivered in the right and left atrium at the right anterior GP and right inferior GP sites. The second TT was performed three months later. Resting heart rate (HR) and heart rate variability parameter (SDDN) were also assessed. Results. At baseline TT, nineteen patients had cardioinhibitory syncope (asystole ranging from 3 to 60 s)  (sinus node arrest – 17 patients, A-V block – 2 patients) and 1 had mixed form of VVS (asystole lasting 3 s preceded by hypotension). During three-month follow-up no syncopal episodes were noted. At the 3-month TT, 6 (30 %) patients had no syncope whereas the remaining 13 (65 %)  had syncope – twelve (60 %) due to vasodepressor mechanism and only one (5 %) due to asystole - as before CNA. One patient did not have TT because of pregnancy. Mean resting HR after CNA was significantly faster and SDNN significantly lower than before the procedure (82 ± 9 vs 69 ± 11 beats/min, p = 0.0004 and 74 ± 22 vs 143 ± 40 ms, p = 0.00003, respectively) and these changes were was similar in those who fainted during second TT and those who did not (82 ± 11 vs 81 ± 4 beats/min, p = NS and (75 ± 2 vs 77 ± 18 ms, p = NS, respectively). Conclusions. CNA profoundly affects the type of VV reaction causing normalization of the response to tilting or changing cardiodepression to vasodepression. These effects are also depicted by changes in HR and heart rate variability. Elimination of TT-induced reflex asystole may prevent clinical recurrences of syncope during short-term follow-up. These findings encourage to conduct further studies involving CNA since this method appears to be effective and obviates the need for pacemaker implantation in young people with reflex asystolic syncope.

scholarly journals Spontaneous Extramural Coronary Arteritis in Dogs,

1989 ◽  
Vol 17 (1_part_2) ◽  
pp. 138-144 ◽  
Author(s):  
Howard A. Hartman
Keyword(s):  
Coronary Arteries ◽  
Inflammatory Cell ◽  
Mononuclear Cells ◽  
Coronary Vessels ◽  
Inflammatory Lesion ◽  
Vascular Lesions ◽  
Coronary Arteritis ◽  
Random Source ◽  
The Media ◽  
The Right

Control and treated beagle and random-source dog hearts obtained from 119 toxicological experiments were evaluated histologically to study the incidence and characteristics of a microscopic inflammatory lesion specific to the extramural coronary arteries. The lesion occurred in 23% of the experiments. The incidence was 2.3% of the control and treated beagle hearts examined. In the control begales, it was present in 3.1% of males and 1.3% of females and in the treated beagles, in 1.8% males and 2.8% females. It occurred in 4.7% of the random-source animals. While not visible grossly, histologically, the solitary lesions were characterized by adventitial infiltrates of mononuclear cells, occasional areas of necrosis with inflammatory cell infiltrates occurring in the mural and subendothelial regions. The latter resulted in prominent separation of the intima from the media. The lesions occurred in the right and left coronary arteries and in the dorsal, circumflex and ventral descending branches of the left coronary artery. Similar vascular lesions were not found in the intramural coronary vessels or in other organs in the affected animals. Expanded sampling of the extramural coronary arteries revealed an incidence of 5–9%. This lesion of focal extramural coronary arteritis was considered idiopathic, and not a manifestation of recently reported polyarteritis syndromes in dogs.

Dynamics of heart rate response to sympathetic nerve stimulation

1998 ◽  
Vol 275 (3) ◽  
pp. H995-H1001 ◽  
Author(s):  
Abdelkader Mokrane ◽  
Réginald Nadeau
Keyword(s):  
Heart Rate ◽  
Time Constant ◽  
Nerve Stimulation ◽  
Sympathetic Nerve ◽  
Neural Control ◽  
Sinus Node ◽  
Mean Delay ◽  
Norepinephrine Concentration ◽  
The Right

Electrical stimulation of the right cardiac sympathetic nerve was used to achieve a step increase of norepinephrine concentration at the sinus node. The heart rate (HR) response to sympathetic stimulation was characterized by a first-order process with a time delay. For moderate to high intensities of stimulation the mean delay and time constant were 0.7 and 2.1 s, respectively, and for low intensities of stimulation they were 0.4 and 1.1 s, respectively. From the analysis of the HR response to different patterns of nerve stimulation, in vivo neurotransmitter kinetics were estimated. The time constant of norepinephrine dissipation averaged ∼9 s. These results combined with computer simulations revealed two facets of sympathetic neural control of HR: 1) negligible role of the sympathetic system in beat-to-beat regulation of HR under stationary conditions and 2) ability of HR to react relatively quickly (within a few seconds) to sharp increases in sympathetic nerve traffic.

scholarly journals Idiopathic Extramural Coronary Arteritis in Beagle and Mongrel Dogs

1987 ◽  
Vol 24 (6) ◽  
pp. 537-544 ◽  
Author(s):  
H. A. Hartman
Keyword(s):  
Coronary Arteries ◽  
Left Coronary Artery ◽  
Inflammatory Cell ◽  
Mononuclear Cells ◽  
Coronary Vessels ◽  
Vascular Lesions ◽  
Elastic Membrane ◽  
Inflammatory Lesions ◽  
Coronary Arteritis ◽  
The Right

Hearts obtained from 119 toxicological experiments on dogs during a 21-year period (1965–1986) were evaluated histologically to determine the incidence and characteristics of focal microscopic inflammatory lesions of the extramural coronary arteries. Lesions were encountered in 23% of 119 experiments. The average overall incidence was 2.3% of 1,905 control and chemically treated male and female beagle hearts (3.1% of male and 1.3% of female control beagles, and 1.8% of male and 2.8% of female treated beagles). Lesions were seen in 4.7% of 127 random-source mongrel dogs. Histologically, lesions were characterized by adventitial infiltrates of mononuclear cells, areas of mural necrosis, and inflammatory cell infiltrates in both mural and subendothelial regions. In the latter region, fibrosis developed separating the intima from the internal elastic membrane. Lesions occurred in the right and left coronary arteries and in the dorsal, circumflex, and ventral descending branches of the left coronary artery. Vascular lesions were not present in the intramural coronary vessels or in vessels of other organs in affected animals. More extensive sampling of the extramural coronary arteries revealed an incidence of 5–9%. The lesion of focal extramural coronary arteritis was idiopathic, and not a manifestation of the polyarteritis syndrome of dogs.

scholarly journals All four coronary arteries arising separately from the right aortic sinus of Valsalva: rare anomaly

2019 ◽  
Vol 12 (4) ◽  
pp. e229498
Author(s):  
Raghvendra Choudhary ◽  
Aditya Batra ◽  
Vinay Malik ◽  
Kunal Mahajan
Keyword(s):  
Coronary Arteries ◽  
Sinus Of Valsalva ◽  
Aortic Sinus ◽  
Rare Anomaly ◽  
The Right

scholarly journals Electroangiographic Correlation of Simultaneous ST-Segment Elevations of Anterior and Inferior Segment: Who Is the Culprit?

2021 ◽  
pp. 263246362110155
Author(s):  
Pankaj Jariwala ◽  
Shanehyder Zaidi ◽  
Kartik Jadhav
Keyword(s):  
Myocardial Infarction ◽  
Coronary Angiography ◽  
Coronary Arteries ◽  
Index Case ◽  
St Segment Elevation ◽  
Segment Elevation Myocardial Infarction ◽  
St Segment ◽  
Inferior Segment ◽  
The Right ◽  
Proximal Occlusion

Simultaneous ST-segment elevation (SST-SE) in anterior and inferior leads in the setting of ST-segment elevation myocardial infarction is often confounding for a cardiologist and further more challenging is the angiographic localization of the culprit vessel. SST-SE can be fatal as it jeopardizes simultaneously a larger area of myocardium. This phenomenon could be due to “one lesion, one artery,” “two lesions, one artery,” “two lesions, two arteries,” or combinations in two different coronary arteries. We have discussed an index case where we encountered a phenomenon of SST-SE and coronary angiography demonstrated “two lesions, one artery” (proximal occlusion and distal critical diffuse stenoses of the wrap-around left anterior descending [LAD] artery) and “two lesions, two (different coronary) arteries” (previously mentioned stenoses of the LAD artery and critical stenosis of the posterolateral branch of the right coronary arteries). We have also described in brief the possible causes of this phenomena and their electroangiographic correlation of the culprit vessels.

scholarly journals RNAseq shows an all-pervasive day-night rhythm in the transcriptome of the pacemaker of the heart

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yanwen Wang ◽  
Cali Anderson ◽  
Halina Dobrzynski ◽  
George Hart ◽  
Alicia D’Souza ◽  
...  
Keyword(s):  
Heart Rate ◽  
Nervous System ◽  
Circadian Clock ◽  
Sick Sinus Syndrome ◽  
Sinus Node ◽  
Signalling Pathways ◽  
Resting Heart Rate ◽  
Ion Channel Regulation ◽  
Channel Regulation ◽  
Physiological Systems

AbstractPhysiological systems vary in a day-night manner anticipating increased demand at a particular time. Heart is no exception. Cardiac output is primarily determined by heart rate and unsurprisingly this varies in a day-night manner and is higher during the day in the human (anticipating increased day-time demand). Although this is attributed to a day-night rhythm in post-translational ion channel regulation in the heart’s pacemaker, the sinus node, by the autonomic nervous system, we investigated whether there is a day-night rhythm in transcription. RNAseq revealed that ~ 44% of the sinus node transcriptome (7134 of 16,387 transcripts) has a significant day-night rhythm. The data revealed the oscillating components of an intrinsic circadian clock. Presumably this clock (or perhaps the master circadian clock in the suprachiasmatic nucleus) is responsible for the rhythm observed in the transcriptional machinery, which in turn is responsible for the rhythm observed in the transcriptome. For example, there is a rhythm in transcripts responsible for the two principal pacemaker mechanisms (membrane and Ca2+ clocks), transcripts responsible for receptors and signalling pathways known to control pacemaking, transcripts from genes identified by GWAS as determinants of resting heart rate, and transcripts from genes responsible for familial and acquired sick sinus syndrome.

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