Effects of 2-[p-(Dimethylamino)Styrl] PyridineMethiodide on Slow Response Action Potentialand Slow lnward Current of Guinea PigPapillary Muscles

The effects of 2-[p-(Dimethylamino)styryl] pyridine methiodide(DSPM)on slow response action potential(SRAP)and slow inward current(Isi) of guinea pig papillary muscles were studied by intracellular microelectrodes and voltage clamp techniques.The APA and V_(max) of SRAP induced by high K￣+were decreased after 50 min of perfusion with DSPM solu- tion. Isi was suppressed from a peak value of8.8± 1.6μA to 5.7± 1.8μA, The results indicated that DSPM has a selective blocking effect on calcium channel.

Effects of hexametazidine on physiological properties of guinea-pig papillary muscles

Effects of hexametazidine [1,4-di(2,3,4-trimethoxybenzyl)piperazine] on the physiological properties of guinea-pig papillary muscles were investigated. Hexametazidine possesses a concentration-dependent negative inotropic effect (IC_(50)=81.8±16.9μmol/L).The effect of hexametazidine(30.8μmol/L)was antago- nized completely by increasing the concentration of Ca^(2+)from 1.8 to 5.4mmol/L. Hexametazidine(30.8μmol/L)increased the threshold concentration of adrenaline for inducing the automaticity of the muscles from 3.95±1.80 to 6.67±4.84μmol/L (P<0.05).It prolonged the functional refractory period from 218±14 to 254±20ms (P<0.05)at the concentration of 61.6μmol/L.Hexametazidine(6.2μmol/L)antago- nized the positive inotropic effect of isoprenaline competitively and of histamine non-competitively(pA 2 and pD2′ values were 5.45 and 4.13, respectively).

NEGATIVE EFFECTS OF ETHANOL ON ISOLATED GUINEA PIG LEFT ATRIUM AND PAPILLARY MUSCLES

Objective To investigate the effects of ethanol on physiological characteristics of the isolated guinea pig left atrium and papillary muscles.Methods The effects of ethanol on contractility, post-rest potentiation and positive staircase phenomenon were observed in isolated left atrium and papillary muscles of guinea pig.Results Ethanol(50.0,100.0,200.0mmol·L -1)prominently inhibited the contraction of papillary muscles. Ethanol(12.5,25.0,50.0,100.0,200.0mmol·L -1) inhibited the contraction of left atrium, and markedly decreased the post-rest potentiation of myocardial contractility in left atrium. High concentration of ethanol(100,200mmol·L -1) depressed the positive staircase phenomenon of isolated guinea pig left atrium.Conclusion These results suggest that ethanol induces inhibitory effects of the contractility, post-rest potentiation, positive staircase phenomenon of left atrium. The mechanism by which ethanol induces the negative inotropic effects may be related to decrease the amount of calcium released from the intracellular stores.

Lesson Eighty four Ventricular arrhythmias originating from papillary muscles in the right ventricle

Patientcharacteristics Patients in this study consisted of eight consecutive patients with frequent premature ventricular complexes(PVCs) or both PVCs and ventricular tachycardia(VT)who had been referred for catheter ablation and whose arrhythmia was mapped to one of the right ventricular(RV)papillary muscles(PAPs).The control group consisted of 10 consecutive patients who were referred for ablation of symptomatic idiopathic

EFFECTS OF DISMERINONE ON HIGH K~＋ DEPOLARIZED SLOW RESPONSE ACTION POTENTIALS IN GUINEA PIG PAPILLARY MUSCLES

The effects of dismerinone (DMR), a derivative of milrinone, on high K+ depolarized slow response action potentials (APs) and intracellular cAMP levels were studied in guinea pig papillary muscles. DMR induced slow APs in high K+ depolorized guinea pig papillary muscles and increased APA, Vmaxand APD50 of the slow APs in dose dependent way ; cAMP levels in same preparations were elevated by DMR. These effects of DMR are similar to isoprenaline (ISO). Bead adrenocepter blocker propranolol had no influence on DMR effect. Overall, the results from this study suggested that effects of DMR were not related to Beta adrenocepter, and might be related to its inhibiting phosphodiesterase Ⅲ(PDE Ⅲ) action.

Delayed papillary muscle rupture after radiofrequency catheter ablation: A case report

BACKGROUND With an increased number of surgical procedures involving the mitral annular region,the risk of mitral valve prolapse(MVP)has also increased.Previous studies have reported that worsening of MVP occurred early after radiofrequency catheter ablation(RFCA)at papillary muscles in ventricular tachycardia(VT)patients with preoperative MVP.CASE SUMMARY We report a case where MVP and papillary muscle rupture occurred 2 wk after RFCA in a papillary muscle originated VT patient without mitral valve regurgitation or prolapse before.The patient then underwent mitral valve replacement with no premature ventricular contraction or VT.During the surgery,a papillary muscle rupture was identified.Pathological examination showed necrosis of the papillary muscle.The patient recovered after mitral valve replacement.CONCLUSION Too many ablation procedures and energy should be avoided.

Contractility detection of isolated mouse papillary muscle using myotronic Myostation-Intact device

Background:To understand the relationship between myocardial contractility and ex-ternal stimuli,detecting ex vivo myocardial contractility is necessary.Methods:We elaborated a method for contractility detection of isolated C57 mouse papillary muscle using Myostation-Intact system under different frequencies,volt-ages,and calcium concentrations.Results:The results indicated that the basal contractility of the papillary muscle was 0.27±0.03 mN at 10 V,500-ms pulse duration,and 1 Hz.From 0.1 to 1.0 Hz,con-tractility decreased with an increase in frequency(0.45±0.11-0.10±0.02 mN).The voltage-initiated muscle contractility varied from 3 to 6 V,and the contractility gradu-ally increased as the voltage increased from 6 to 10 V(0.14±0.02-0.28±0.03 mN).Moreover,the muscle contractility increased when the calcium concentration was increased from 1.5 to 3 mM(0.45±0.17-1.11±0.05 mN);however,the contractility stopped increasing even when the concentration was increased to 7.5 mM(1.02±0.23 mN).Conclusions:Our method guaranteed the survivability of papillary muscle ex vivo and provided instructions for Myostation-Intact users for isolated muscle contractility investigations.

Papillary Muscle Relocation in Secondary Mitral Regurgitation: Midterm Outcomes

Background: Mitral valve repair in secondary mitral regurgitation is still uncertain as the chance of recurrence is approximately 30 percent after solely undersized annuloplasty. Some procedures adding to the subvalvular level are proposed to alleviate the recurrent rate. This study was to evaluate the clinical and echocardiographic outcomes of papillary muscle relocation plus undersized ring in secondary mitral regurgitation (2nd MR). Methods: Medical records of moderate to severe 2nd MR with tethering depth of more than 1 cm patients who underwent papillary muscle relocation plus undersized ring from 2014 to 2020 were reviewed. Clinical and echocardiographic parameters before and after operation were analyzed. Results: Thirty-two patients were included during the 6-year period. There was no perioperative mortality. Two patients died at one year from ischemic stroke and car accidents with overall 5-year survival of 93.7%. All patients were in NYHA class I and II with MR grading as trivial or mild at a median follow-up of 33 months. Postoperative mean tenting depth, area and posterior leaflet angle decreased remarkably from 1.18 cm, 2.61 cm2 and 46.5 degree to 0.65 cm, 1.22 cm2 and 28.6 degree, respectively (p 0.001, 0.02, and 0.01). Moreover, left ventricular function and remodeling were also notably improved (EF;38.2% vs 49.1%: p = 0.018, LVEDD;62.8 vs 54.6 mm: p = 0.005, LVESD;50.2 vs 42.4 mm: p = 0.01). Conclusions: Papillary muscle relocation combined with undersized annuloplasty improved mid-term clinical outcomes. Apart from reduction of recurrent MR rate, restoration of mitral configuration and reverse LV remodeling could be the effect of adding subvalvular correction in this pathology.

THE INFLUENCE OF SAPONINS OF PANAX QUINQUEFOLIUM LEAF AND STEM ON THE SLOW ACTION POTENTIALS IN MYOCARDIUM

The effects of Saponins of Panax Quinquefolium Leaf and Stem(SPQLS)were evaluatedin the rabbit sinus node and in the guinea pig papillary muscles both showing slow responses in high[k+].and being exposed to 0.3 μmol/L verapamil using conventional microelcctrode technique.Inthe sinus node, SPQLS 100 mg/L decreased the APA and Vmax.At the concentration of 200 mg/L,in addition to further depressing the upotroke,SPQIS decreased the SP4,shortened the APD and prolonged the SCL.In the guinea Pig papillary muscle,SPQLS shortened the APD and decreased theAPA as well as Vmax in high[k+3].When verapamil was exposed to the normal Tyrode's solution,SPQLS depressed the upstroke without-affecting the APD in the guinea pig papillary muscle.Thesefindings suggest that SPQLS exerted a blockade effect on the transmembrane Ca2+ influx and Na+ influx in myocardium.

Effects of Electric Stimulations Applied During Absolute Refractory Period on Ventricular Muscle from Rabbits

Objectives To investigate the influences of electric signals applied during absolute refractory period (ARP) on the contractility of isolated papillary muscle from rabbits. Methods Papillary muscle was exercised from the right ventricle and was paced at 1 Hz. Biphasic square wave current pulse was delivered during the absolute refractory period (called CCM) in isolated, superfused, isometrically contractility rabbit papillary muscle. The peak tension (PT) of papillary muscle, as well as maximum positive tension change ( + dT/dtmax), were observed. Results Compared with the baseline, both PT and + dT/dtmax significantly increased during CCM stimulation by 18.2% and 21.4% respectively (P < 0. 05) . In addition, PT increased significantly with one or two beats following CCM signal application and reached a. new steady state level after a few beats. Once the CCM signals were turned off, the PT returned to the approximately baseline level ( P < 0. 05). Moreover, the effect of CCM on PT was dose - response to voltage. The obvious effect was at higher voltage. No effect was observed at lower voltage. Conclusions Electric signals delivered during the absolute refractory period can rapidly enhance the contractility of myocardium, which suggests that CCM signal is a novel potent method for contractility modulation.