Araştırma Makalesi
BibTex RIS Kaynak Göster

Yaşlı Hemodiyaliz Hastalarının Elektrokardiyografisinde Tp-e Aralığının ve Elektrolit Bozuklukları ile İlişkisinin Değerlendirilmesi

Yıl 2021, , 194 - 200, 29.05.2021
https://doi.org/10.21673/anadoluklin.790495

Öz

Amaç: Aritmilere bağlı ani kardiyak ölüm (AKÖ), yaşlı hemodiyaliz (HD) hastalarında başlıca ölüm nedenlerindendir. Elektrokardiyografide (EKG) uzamış Tp-e aralığı (Tpe) ve artmış Tpe/QTc oranı ile AKÖ arasında güçlü bir ilişki olduğu bulunmuştur. Bu çalışmada serum elektrolit düzeylerindeki de¬ğişikliklerin HD öncesi ve sonrası EKG parametreleri, özellikle de Tpe üzerindeki etkilerini araştırmak amaçlanmıştır.


Yöntem:
Çalışma (QT aralığını etkilediği bilinen bir hastalığı veya ilaç kullanımı olmayan) 160 HD hastası ve normal böbrek fonksiyonlarına sahip, yaş ve cinsiyet uyumlu 80 kontrol içerdi. Tüm katılımcılar 55 yaş ve üzeri idi. HD öncesi ve sonrası serum elektrolit değerleri ve EKG kayıtları elde edildi. Kalp hızı, QRS aralığı, QTc, Tpe ve Tpe/QTc değerleri hesaplandı. HD öncesi veriler, HD sonrası veriler ve kontroller ile karşılaştırıldı.


Bulgular:
HD öncesi ve sonrası Tpe (iki karşılaştırma için de p<0,001) ve Tpe/QTc (sırasıyla p=0,024 ve p<0,001) değerleri kontrol grubuna kıyasla HD grubunda anlamlı biçimde daha yüksekti. HD sonrası Tpe ve Tpe/QTc değerleri, HD öncesi değerlere kıyasla anlamlı biçimde artmıştı (her karşı¬laştırma için p<0,001). HD öncesi Tpe, hipokalsemi veya hiperfosfatemili hastalarda normokalsemik ve normofosfatemik hastalara göre daha uzundu (iki veri grubu için de p=0,04). ΔTpe, Δkalsiyum (r=-0,19; p=0,02) ve Δfosfor (r=-0,23; p=0,004) ile anlamlı şekilde koreleydi.


Sonuç:
Yaşlı HD hastalarında HD öncesinde uzamış olan Tpe, HD’den sonra daha da uzamıştı. Hipokalsemi ve hiperfosfatemi buna neden olan faktörlerden olabilir.

Kaynakça

  • Hill NR, Fatoba ST, Oke JL, Hirst JA, O’Callaghan CA, Lasserson DS, et al. Global prevalence of chronic kidney disease—a systematic review and meta-analysis. PloS One. 2016;11(7):e0158765.
  • Green D, Roberts PR, New DI, Kalra PA. Sudden cardiac death in hemodialysis patients: an in-depth review. Am J Kidney Dis. 2011;57(6):921–9.
  • Makar MS, Pun PH. Sudden cardiac death among hemo¬dialysis patients. Am J Kidney Dis. 2017;69(5):684–95.
  • Eckart RE, Shry EA, Burke AP, McNear JA, Appel DA, Castillo-Rojas LM, et al. Sudden death in young adults: an autopsy-based series of a population undergoing ac¬tive surveillance. J Am Coll Cardiol. 2011;58(12):1254– 61.
  • Nishimura M, Nakayama K, Ishikawa Y. Cardiac ar¬rhythmias caused by electrolyte imbalance [article in Japanese]. Nihon Rinsho. 1996;54(8):2207–12.
  • Stewart GA, Gansevoort RT, Mark PB, Rooney E, Mc¬Donagh TA, Dargie HJ, et al. Electrocardiographic ab¬normalities and uremic cardiomyopathy. Kidney Int. 2005;67(1):217–26.
  • Bleyer AJ, Hartman J, Brannon PC, Reeves-Daniel A, Satko SG, Russell G. Characteristics of sudden death in hemodialysis patients. Kidney Int. 2006;69(12):2268–73.
  • Panikkath R, Reinier K, Uy-Evanado A, Teodorescu C, Hattenhauer J, Mariani R, et al. Prolonged Tpeak-to-tend interval on the resting ECG is associated with increased risk of sudden cardiac death. Circ Arrhythm Electrophysiol. 2011;4(4):441–7.
  • Antzelevitch C, Shimizu W, Yan GX, Sicouri S, Weissen¬burger J, Nesterenko VV, et al. The M cell: its contribu¬tion to the ECG and to normal and abnormal electri¬cal function of the heart. J Cardiovasc Electrophysiol. 1999;10(8):1124–52.
  • Hevia JC, Antzelevitch C, Barzaga FT, Sanchez MD, Balea FD, Molina RZ, et al. Tpeak-Tend and Tpeak-Tend dispersion as risk factors for ventricular tachycardia/ ventricular fibrillation in patients with the Brugada syn¬drome. J Am Coll Cardiol. 2006;47(9):1828–34.
  • Erikssen G, Liestol K, Gullestad L, Haugaa KH, Ben¬dz B, Amlie JP. The terminal part of the QT interval (T peak to T end): a predictor of mortality after acute myocardial infarction. Ann Noninvasive Electrocardiol. 2012;17(2):85–94.
  • Jaroszynski AJ, Zaluska WT, Ksiazek A. Effect of hae¬modialysis on regional and transmural inhomogeneities of the ventricular repolarisation phase. Nephron Clin Pract. 2005;99(1):c24–30.
  • Ozportakal H, Ozkok A, Alkan O, Bulut AS, Boyraz M, Inanir M, et al. Hemodialysis-induced repolarization abnormalities on ECG are influenced by serum calcium levels and ultrafiltration volumes. Int Urol Nephrol. 2017;49(3):509–15.
  • Grassmann A, Gioberge S, Moeller S, Brown G. ESRD patients in 2004: global overview of patient numbers, treatment modalities and associated trends. Nephrol Dial Transplant. 2005;20(12):2587–93.
  • Uda S, Mizobuchi M, Akizawa T. Biocompatible char¬acteristics of high-performance membranes. Contrib Nephrol. 2011;173:23–9.
  • Chandrashekar A, Ramakrishnan S, Rangarajan D. Sur¬vival analysis of patients on maintenance hemodialysis. Indian J Nephrol. 2014;24(4):206–13.
  • Rodriguez-Benot A, Martin-Malo A, Alvarez-Lara MA, Rodriguez M, Aljama P. Mild hyperphosphatemia and mortality in hemodialysis patients. Am J Kidney Dis. 2005;46(1):68–77.
  • Severi S, Grandi E, Pes C, Badiali F, Grandi F, Santoro Hill NR, Fatoba ST, Oke JL, Hirst JA, O’Callaghan CA, Lasserson DS, et al. Global prevalence of chronic kidney disease—a systematic review and meta-analysis. PloS One. 2016;11(7):e0158765.
  • Abe S, Yoshizawa M, Nakanishi N, Yazawa T, Yokota K, Honda M, et al. Electrocardiographic abnormalities in patients receiving hemodialysis. Am Heart J. 1996;131(6):1137–44.
  • Shapira OM, Bar-Khayim Y. ECG changes and cardiac arrhythmias in chronic renal failure patients on hemodialysis. J Electrocardiol. 1992;25(4):273–9.
  • Kalantzi K, Gouva C, Letsas KP, Vlachopanou A, Foulidis V, Bechlioulis A, et al. The impact of hemodialysis on the dispersion of ventricular repolarization. Pacing Clin Electrophysiol. 2013;36(3):322–7.
  • Sivri S, Celik M. Evaluation of index of cardiac-electrophysiological balance before and after hemodialysis in patients with end-stage renal disease. J Electrocardiol. 2019;54:72–5.
  • Tokatli A, Kilicaslan F, Alis M, Yiginer O, Uzun M. Prolonged Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio in patients with type 2 diabetes mellitus. Endocrinol Metab. 2016;31(1):105–12.
  • Akboga MK, Gulcihan Balci K, Yilmaz S, Aydin S, Yayla C, Ertem AG, et al. Tp-e interval and Tp-e/QTc ratio as novel surrogate markers for prediction of ventricular arrhythmic events in hypertrophic cardiomyopathy. Anatol J Cardiol. 2017;18(1):48–53.
  • Gurdal A, Eroglu H, Helvaci F, Sumerkan MC, Kasali K, Cetin S, et al. Evaluation of Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio in patients with subclinical hypothyroidism. Ther Adv Endocrinol Metab. 2017;8(3):25–32.
  • Covic A, Diaconita M, Gusbeth-Tatomir P, Covic M, Botezan A, Ungureanu G, et al. Haemodialysis increases QT(c) interval but not QT(c) dispersion in ESRD patients without manifest cardiac disease. Nephrol Dial Transplant. 2002;17(12):2170–7.
  • Severi S, Ciandrini A, Grandi E, Cavalcanti S, Bini S, Badiali F, et al. Cardiac response to hemodialysis with different cardiovascular tolerance: heart rate variability and QT interval analysis. Hemodial Int. 2006;10(3):287–93.
  • Astan R, Akpinar I, Karan A, Kacmaz F, Sokmen E, Baysal E, et al. The effect of hemodialysis on electrocardiographic parameters. Ann Noninvasive Electrocardiol. 2015;20(3):253–7.
  • Drighil A, Madias JE, Benjelloun M, Kamoum H, Bennis A, Azzouzi L, et al. Changes in the QT intervals, QT dispersion, and amplitude of T waves after hemodialysis. Ann Noninvasive Electrocardiol. 2007;12(2):137–44.
  • Alabd MA, El-Hammady W, Shawky A, Nammas W, El- Tayeb M. QT interval and QT dispersion in patients undergoing hemodialysis: revisiting the old theory. Nephron Extra. 2011;1(1):1–8.
  • Kulmatycki KM, Abouchehade K, Sattari S, Jamali F. Drug-disease interactions: reduced beta-adrenergic and potassium channel antagonist activities of sotalol in the presence of acute and chronic inflammatory conditions in the rat. Br J Pharmacol. 2001;133(2):286–94.
  • Murasawa T, Sakai Y, Sakai S, Ohtsuka T, Ohno D, Amitani K, et al. QT dispersion increases during hemodialysis procedures in patients undergoing maintenance dialysis: association with an RA system and Holter electrocardiogram. Nihon Jinzo Gakkai Shi. 2008;50(4):481–7.
  • Tang WH, Wang CP, Chung FM, Huang LL, Yu TH, Hung WC, et al. Uremic retention solute indoxyl sulfate level is associated with prolonged QTc interval in early CKD patients. PloS One. 2015;10(3):e0119545.
  • Nappi SE, Virtanen VK, Saha HH, Mustonen JT, Pasternack AI. QTc dispersion increases during hemodialysis with low-calcium dialysate. Kidney Int. 2000;57(5):2117–22.
  • Yetkin E, Ileri M, Tandogan I, Boran M, Yanik A, Hisar I, et al. Increased QT interval dispersion after hemodialysis: role of peridialytic electrolyte gradients. Angiology. 2000;51(6):499–504.
  • Slatopolsky E. New developments in hyperphosphatemia management. J Am Soc Nephrol. 2003;14(9 Suppl 4):S297–9.
  • Savica V, Calo LA, Monardo P, Santoro D, Bellinghieri G. Phosphate binders and management of hyperphosphataemia in end-stage renal disease. Nephrol Dial Transplant. 2006;21(8):2065–8.
  • Imanishi Y, Inaba M, Nakatsuka K, Nagasue K, Okuno S, Yoshihara A, et al. FGF-23 in patients with end-stage renal disease on hemodialysis. Kidney Int. 2004;65(5):1943–6.
  • Amann K, Tornig J, Kugel B, Gross ML, Tyralla K, El-Shakmak A, et al. Hyperphosphatemia aggravates cardiac fibrosis and microvascular disease in experimental uremia. Kidney Int. 2003;63(4):1296–301.
  • Wang Q, Cui Y, Yogendranath P, Wang N. Blood pressure and heart rate variability are linked with hyperphosphatemia in chronic kidney disease patients. Chronobiol Int. 2018;35(10):1329–34.

An Evaluation of Tp-e Interval and its Associations with Electrolyte Imbalances in the Electrocardiography of Elderly Patients on Hemodialysis

Yıl 2021, , 194 - 200, 29.05.2021
https://doi.org/10.21673/anadoluklin.790495

Öz

Aim: Sudden cardiac death (SCD) due to arrhythmias is a major cause of death in elderly patients on hemodialysis (HD). It has been found that prolonged Tp-e interval (Tpe) on electrocardiography (ECG) and increased Tpe/QTc ratio are strongly associated with SCD. In this study, we aimed to inves¬tigate the effects of changes in serum electrolyte levels on the pre- and post-HD ECG parameters, particularly Tpe.

Methods: The study included 160 HD patients (with no disease or medication known to affect the QT interval) and 80 age- and sex-matched controls with normal kidney functions. All participants were aged 55 years or older. Pre- and post-HD serum electrolyte values and ECG re¬cordings were obtained. The heart rate, QRS interval, QTc, Tpe, and Tpe/QTc values were calculated. The pre-HD data were compared with the post-HD data as well as with controls.


Results:
The pre- and post-HD Tpe (p<0.001 for both comparisons) and Tpe/QTc (p=0.024 and p<0.001, respectively) values were significantly higher in the HD group than in the control group. The post-HD Tpe and Tpe/QTc values were significantly increased compared to the pre-HD values (p<0.001 for each comparison). The pre-HD Tpe was longer in patients with hypocalcemia or hy¬perphosphatemia than in normocalcemic and normophosphatemic patients (p=0.04 for both data¬sets). ΔTpe was significantly correlated with Δcalcium (r=-0.19, p=0.02) and Δphosphorus (r=-0.23, p=0.004).


Conclusion
: In the elderly patients on HD, Tpe, which was prolonged before HD, was even more prolonged after HD. Hypocalcemia and hyperphosphatemia may be among the un¬derlying factors.

Kaynakça

  • Hill NR, Fatoba ST, Oke JL, Hirst JA, O’Callaghan CA, Lasserson DS, et al. Global prevalence of chronic kidney disease—a systematic review and meta-analysis. PloS One. 2016;11(7):e0158765.
  • Green D, Roberts PR, New DI, Kalra PA. Sudden cardiac death in hemodialysis patients: an in-depth review. Am J Kidney Dis. 2011;57(6):921–9.
  • Makar MS, Pun PH. Sudden cardiac death among hemo¬dialysis patients. Am J Kidney Dis. 2017;69(5):684–95.
  • Eckart RE, Shry EA, Burke AP, McNear JA, Appel DA, Castillo-Rojas LM, et al. Sudden death in young adults: an autopsy-based series of a population undergoing ac¬tive surveillance. J Am Coll Cardiol. 2011;58(12):1254– 61.
  • Nishimura M, Nakayama K, Ishikawa Y. Cardiac ar¬rhythmias caused by electrolyte imbalance [article in Japanese]. Nihon Rinsho. 1996;54(8):2207–12.
  • Stewart GA, Gansevoort RT, Mark PB, Rooney E, Mc¬Donagh TA, Dargie HJ, et al. Electrocardiographic ab¬normalities and uremic cardiomyopathy. Kidney Int. 2005;67(1):217–26.
  • Bleyer AJ, Hartman J, Brannon PC, Reeves-Daniel A, Satko SG, Russell G. Characteristics of sudden death in hemodialysis patients. Kidney Int. 2006;69(12):2268–73.
  • Panikkath R, Reinier K, Uy-Evanado A, Teodorescu C, Hattenhauer J, Mariani R, et al. Prolonged Tpeak-to-tend interval on the resting ECG is associated with increased risk of sudden cardiac death. Circ Arrhythm Electrophysiol. 2011;4(4):441–7.
  • Antzelevitch C, Shimizu W, Yan GX, Sicouri S, Weissen¬burger J, Nesterenko VV, et al. The M cell: its contribu¬tion to the ECG and to normal and abnormal electri¬cal function of the heart. J Cardiovasc Electrophysiol. 1999;10(8):1124–52.
  • Hevia JC, Antzelevitch C, Barzaga FT, Sanchez MD, Balea FD, Molina RZ, et al. Tpeak-Tend and Tpeak-Tend dispersion as risk factors for ventricular tachycardia/ ventricular fibrillation in patients with the Brugada syn¬drome. J Am Coll Cardiol. 2006;47(9):1828–34.
  • Erikssen G, Liestol K, Gullestad L, Haugaa KH, Ben¬dz B, Amlie JP. The terminal part of the QT interval (T peak to T end): a predictor of mortality after acute myocardial infarction. Ann Noninvasive Electrocardiol. 2012;17(2):85–94.
  • Jaroszynski AJ, Zaluska WT, Ksiazek A. Effect of hae¬modialysis on regional and transmural inhomogeneities of the ventricular repolarisation phase. Nephron Clin Pract. 2005;99(1):c24–30.
  • Ozportakal H, Ozkok A, Alkan O, Bulut AS, Boyraz M, Inanir M, et al. Hemodialysis-induced repolarization abnormalities on ECG are influenced by serum calcium levels and ultrafiltration volumes. Int Urol Nephrol. 2017;49(3):509–15.
  • Grassmann A, Gioberge S, Moeller S, Brown G. ESRD patients in 2004: global overview of patient numbers, treatment modalities and associated trends. Nephrol Dial Transplant. 2005;20(12):2587–93.
  • Uda S, Mizobuchi M, Akizawa T. Biocompatible char¬acteristics of high-performance membranes. Contrib Nephrol. 2011;173:23–9.
  • Chandrashekar A, Ramakrishnan S, Rangarajan D. Sur¬vival analysis of patients on maintenance hemodialysis. Indian J Nephrol. 2014;24(4):206–13.
  • Rodriguez-Benot A, Martin-Malo A, Alvarez-Lara MA, Rodriguez M, Aljama P. Mild hyperphosphatemia and mortality in hemodialysis patients. Am J Kidney Dis. 2005;46(1):68–77.
  • Severi S, Grandi E, Pes C, Badiali F, Grandi F, Santoro Hill NR, Fatoba ST, Oke JL, Hirst JA, O’Callaghan CA, Lasserson DS, et al. Global prevalence of chronic kidney disease—a systematic review and meta-analysis. PloS One. 2016;11(7):e0158765.
  • Abe S, Yoshizawa M, Nakanishi N, Yazawa T, Yokota K, Honda M, et al. Electrocardiographic abnormalities in patients receiving hemodialysis. Am Heart J. 1996;131(6):1137–44.
  • Shapira OM, Bar-Khayim Y. ECG changes and cardiac arrhythmias in chronic renal failure patients on hemodialysis. J Electrocardiol. 1992;25(4):273–9.
  • Kalantzi K, Gouva C, Letsas KP, Vlachopanou A, Foulidis V, Bechlioulis A, et al. The impact of hemodialysis on the dispersion of ventricular repolarization. Pacing Clin Electrophysiol. 2013;36(3):322–7.
  • Sivri S, Celik M. Evaluation of index of cardiac-electrophysiological balance before and after hemodialysis in patients with end-stage renal disease. J Electrocardiol. 2019;54:72–5.
  • Tokatli A, Kilicaslan F, Alis M, Yiginer O, Uzun M. Prolonged Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio in patients with type 2 diabetes mellitus. Endocrinol Metab. 2016;31(1):105–12.
  • Akboga MK, Gulcihan Balci K, Yilmaz S, Aydin S, Yayla C, Ertem AG, et al. Tp-e interval and Tp-e/QTc ratio as novel surrogate markers for prediction of ventricular arrhythmic events in hypertrophic cardiomyopathy. Anatol J Cardiol. 2017;18(1):48–53.
  • Gurdal A, Eroglu H, Helvaci F, Sumerkan MC, Kasali K, Cetin S, et al. Evaluation of Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio in patients with subclinical hypothyroidism. Ther Adv Endocrinol Metab. 2017;8(3):25–32.
  • Covic A, Diaconita M, Gusbeth-Tatomir P, Covic M, Botezan A, Ungureanu G, et al. Haemodialysis increases QT(c) interval but not QT(c) dispersion in ESRD patients without manifest cardiac disease. Nephrol Dial Transplant. 2002;17(12):2170–7.
  • Severi S, Ciandrini A, Grandi E, Cavalcanti S, Bini S, Badiali F, et al. Cardiac response to hemodialysis with different cardiovascular tolerance: heart rate variability and QT interval analysis. Hemodial Int. 2006;10(3):287–93.
  • Astan R, Akpinar I, Karan A, Kacmaz F, Sokmen E, Baysal E, et al. The effect of hemodialysis on electrocardiographic parameters. Ann Noninvasive Electrocardiol. 2015;20(3):253–7.
  • Drighil A, Madias JE, Benjelloun M, Kamoum H, Bennis A, Azzouzi L, et al. Changes in the QT intervals, QT dispersion, and amplitude of T waves after hemodialysis. Ann Noninvasive Electrocardiol. 2007;12(2):137–44.
  • Alabd MA, El-Hammady W, Shawky A, Nammas W, El- Tayeb M. QT interval and QT dispersion in patients undergoing hemodialysis: revisiting the old theory. Nephron Extra. 2011;1(1):1–8.
  • Kulmatycki KM, Abouchehade K, Sattari S, Jamali F. Drug-disease interactions: reduced beta-adrenergic and potassium channel antagonist activities of sotalol in the presence of acute and chronic inflammatory conditions in the rat. Br J Pharmacol. 2001;133(2):286–94.
  • Murasawa T, Sakai Y, Sakai S, Ohtsuka T, Ohno D, Amitani K, et al. QT dispersion increases during hemodialysis procedures in patients undergoing maintenance dialysis: association with an RA system and Holter electrocardiogram. Nihon Jinzo Gakkai Shi. 2008;50(4):481–7.
  • Tang WH, Wang CP, Chung FM, Huang LL, Yu TH, Hung WC, et al. Uremic retention solute indoxyl sulfate level is associated with prolonged QTc interval in early CKD patients. PloS One. 2015;10(3):e0119545.
  • Nappi SE, Virtanen VK, Saha HH, Mustonen JT, Pasternack AI. QTc dispersion increases during hemodialysis with low-calcium dialysate. Kidney Int. 2000;57(5):2117–22.
  • Yetkin E, Ileri M, Tandogan I, Boran M, Yanik A, Hisar I, et al. Increased QT interval dispersion after hemodialysis: role of peridialytic electrolyte gradients. Angiology. 2000;51(6):499–504.
  • Slatopolsky E. New developments in hyperphosphatemia management. J Am Soc Nephrol. 2003;14(9 Suppl 4):S297–9.
  • Savica V, Calo LA, Monardo P, Santoro D, Bellinghieri G. Phosphate binders and management of hyperphosphataemia in end-stage renal disease. Nephrol Dial Transplant. 2006;21(8):2065–8.
  • Imanishi Y, Inaba M, Nakatsuka K, Nagasue K, Okuno S, Yoshihara A, et al. FGF-23 in patients with end-stage renal disease on hemodialysis. Kidney Int. 2004;65(5):1943–6.
  • Amann K, Tornig J, Kugel B, Gross ML, Tyralla K, El-Shakmak A, et al. Hyperphosphatemia aggravates cardiac fibrosis and microvascular disease in experimental uremia. Kidney Int. 2003;63(4):1296–301.
  • Wang Q, Cui Y, Yogendranath P, Wang N. Blood pressure and heart rate variability are linked with hyperphosphatemia in chronic kidney disease patients. Chronobiol Int. 2018;35(10):1329–34.
Toplam 40 adet kaynakça vardır.

Ayrıntılar

Birincil Dil İngilizce
Konular Sağlık Kurumları Yönetimi
Bölüm ORJİNAL MAKALE
Yazarlar

Mustafa Candemir 0000-0002-3645-3912

Mehmet Emin Demir 0000-0003-2491-4926

Burcu Candemir 0000-0003-1800-6235

Serdar Nurkoç Bu kişi benim 0000-0001-6575-9198

Yayımlanma Tarihi 29 Mayıs 2021
Kabul Tarihi 2 Ocak 2021
Yayımlandığı Sayı Yıl 2021

Kaynak Göster

Vancouver Candemir M, Demir ME, Candemir B, Nurkoç S. An Evaluation of Tp-e Interval and its Associations with Electrolyte Imbalances in the Electrocardiography of Elderly Patients on Hemodialysis. Anadolu Klin. 2021;26(2):194-200.

13151 This Journal licensed under a CC BY-NC (Creative Commons Attribution-NonCommercial 4.0) International License.