Electrophysiological and Proarrhythmic Effects of Hydroxychloroquine Challenge in Guinea-Pig Hearts

Abstract

Hydroxychloroquine (HCQ), clinically established in antimalarial and autoimmune therapy, recently raised cardiac arrhythmogenic concerns when used alone or with azithromycin (HCQ+AZM) in Covid-19. We report complementary, experimental, studies of its electrophysiological effects. In patch clamped HEK293 cells expressing human cardiac ion channels, HCQ inhibited I Kr and I K1 at a therapeutic concentrations (IC 50 s: 10 ± 0.6 and 34 ± 5.0 μM). I Na and I CaL showed higher IC 50 s; I to and I Ks were unaffected. AZM slightly inhibited I Na , I CaL, I Ks, and I Kr , sparing I K1 and I to . (HCQ+AZM) inhibited I Kr and I K1 (IC 50 s: 7.7 ± 0.8 and 30.4 ± 3.0 μM), sparing I Na , I CaL , and I to . Molecular induced-fit docking modeling confirmed potential HCQ-hERG but weak AZM-hERG binding. Effects of μM-HCQ were studied in isolated perfused guinea-pig hearts by multielectrode, optical RH237 voltage, and Rhod-2 mapping. These revealed reversibly reduced left atrial and ventricular action potential (AP) conduction velocities increasing their heterogeneities, increased AP durations (APDs), and increased durations and dispersions of intracellular [Ca 2+ ] transients, respectively. Hearts also became bradycardic with increased electrocardiographic PR and QRS durations. The (HCQ+AZM) combination accentuated these effects. Contrastingly, (HCQ+AZM) and not HCQ alone disrupted AP propagation, inducing alternans and torsadogenic-like episodes on voltage mapping during forced pacing. O'Hara-Rudy modeling showed that the observed I Kr and I K1 effects explained the APD alterations and the consequently prolonged Ca 2+ transients. The latter might then downregulate I Na , reducing AP conduction velocity through recently reported I Na downregulation by cytosolic [Ca 2+ ] in a novel scheme for drug action. The findings may thus prompt future investigations of HCQ's cardiac safety under particular, chronic and acute, clinical situations.

Feedback contributions to excitation–contraction coupling in native functioning striated muscle

“…Furthermore, (HCQ+AZM) accentuated all these effects of HCQ. It further disrupted AP propagation and induced alternans and torsades-like episodes during forced pacing (figure 7g) [109].…”

“…Further extensions of hypotheses invoking Ca 2+ -mediated feedback actions on Na v 1.4/Na v 1.5 arise from the reciprocal interactions between surface membrane ion channel activity and Ca 2+ homeostasis [ 109 ]. In addition to variations in upstroke characteristics that result from I Na actions, cardiac muscle APs can vary in their recovery durations (APDs) reflecting modifications in their I K or I Ca .…”

“…Of these, in vitro electrophysiological cultured cell models [ 111 , 112 ] and modelling studies bearing on these drug actions on individual surface membrane ion channels [ 112 , 113 ] predicted potentially pro-arrhythmic behaviour. Experiments integrating biophysical studies of ion channel properties with studies of AP generation and conduction, and of Ca 2+ homeostatic processes in intact hearts together additionally suggested Ca 2+ -mediated feedback actions on AP generation and conduction [ 109 ].…”

“…Furthermore, (HCQ+AZM) accentuated all these effects of HCQ. It further disrupted AP propagation and induced alternans and torsades-like episodes during forced pacing ( figure 7 g ) [ 109 ].

Figure 7 Effects on human (h) Na v 1.5 function following increases in APD secondary to HCQ and AZM challenge.

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“…NS not significant, * p < 0.05, ** p < 0.01, *** p < 0.001. (( a , b ) from figure 3(A,D)(i) and (ii); ( d ) from figure 6(A)(i); ( e )(a–c) and ( f ) from figure 6(B)(i) and (iii), (C)(i) and (iii), and (A)(i) and (iv); ( g ) from figure 7(B,C) of Wang et al [ 109 ] by permission). …”