Editorial comment
Chronotropism during exercise. Methodological and conceptual inconsistencies
Cronotropismo no esforço. Inconsistências metodológicas e conceptuais
Miguel Mendes
Serviço de Cardiologia, CHLO, Hospital de Santa Cruz, Carnaxide, Portugal
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[SpO2: arterial oxygen saturation; ■: without mask; ●: surgical mask; <elsevierMultimedia ident="202112160943504841"></elsevierMultimedia>: respirator; *: signals p<0.05 on comparison of test conditions].</p>" ] ] ] "autores" => array:1 [ 0 => array:2 [ "autoresLista" => "Tiago Pimenta, Helena Tavares, João Ramos, Mafalda Oliveira, David Reis, Hugo Amorim, Afonso Rocha" "autores" => array:7 [ 0 => array:2 [ "nombre" => "Tiago" "apellidos" => "Pimenta" ] 1 => array:2 [ "nombre" => "Helena" "apellidos" => "Tavares" ] 2 => array:2 [ "nombre" => "João" "apellidos" => "Ramos" ] 3 => array:2 [ "nombre" => "Mafalda" "apellidos" => "Oliveira" ] 4 => array:2 [ "nombre" => "David" "apellidos" => "Reis" ] 5 => array:2 [ "nombre" => "Hugo" "apellidos" => "Amorim" ] 6 => array:2 [ "nombre" => "Afonso" "apellidos" => "Rocha" ] ] ] ] ] "idiomaDefecto" => "en" "Traduccion" => array:1 [ "en" => array:9 [ "pii" => "S0870255121004285" "doi" => "10.1016/j.repc.2021.01.017" "estado" => "S300" "subdocumento" => "" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:1 [ "total" => 0 ] "idiomaDefecto" => "en" "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S0870255121004285?idApp=UINPBA00004E" ] ] "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S2174204921003676?idApp=UINPBA00004E" "url" => "/21742049/0000004000000012/v1_202112160943/S2174204921003676/v1_202112160943/en/main.assets" ] "itemAnterior" => array:20 [ "pii" => "S2174204921003664" "issn" => "21742049" "doi" => "10.1016/j.repce.2021.11.013" "estado" => "S300" "fechaPublicacion" => "2021-12-01" "aid" => "1830" "copyright" => "Sociedade Portuguesa de Cardiologia" "documento" => "article" "crossmark" => 1 "licencia" => "http://creativecommons.org/licenses/by-nc-nd/4.0/" "subdocumento" => "fla" "cita" => "Rev Port Cardiol. 2021;40:947-53" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:1 [ "total" => 0 ] "en" => array:13 [ "idiomaDefecto" => true "cabecera" => "<span class="elsevierStyleTextfn">Original Article</span>" "titulo" => "Cardiac rehabilitation and improvement of chronotropic incompetence: Is it the exercise or just the beta blockers?" "tienePdf" => "en" "tieneTextoCompleto" => "en" "tieneResumen" => array:2 [ 0 => "en" 1 => "pt" ] "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "947" "paginaFinal" => "953" ] ] "titulosAlternativos" => array:1 [ "pt" => array:1 [ "titulo" => "Reabilitação cardíaca e melhoria da incompetência cronotrópica: efeito do exercício ou apenas dos beta-bloqueadores?" ] ] "contieneResumen" => array:2 [ "en" => true "pt" => true ] "contieneTextoCompleto" => array:1 [ "en" => true ] "contienePdf" => array:1 [ "en" => true ] "resumenGrafico" => array:2 [ "original" => 0 "multimedia" => array:7 [ "identificador" => "fig0005" "etiqueta" => "Figure 1" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr1.jpeg" "Alto" => 1462 "Ancho" => 2500 "Tamanyo" => 120434 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0055" class="elsevierStyleSimplePara elsevierViewall">Association between conventional chronotropic index change and functional capacity improvement.</p>" ] ] ] "autores" => array:1 [ 0 => array:2 [ "autoresLista" => "Tiago Pimenta, J. Afonso Rocha" "autores" => array:2 [ 0 => array:2 [ "nombre" => "Tiago" "apellidos" => "Pimenta" ] 1 => array:2 [ "nombre" => "J. Afonso" "apellidos" => "Rocha" ] ] ] ] ] "idiomaDefecto" => "en" "Traduccion" => array:1 [ "en" => array:9 [ "pii" => "S0870255121004248" "doi" => "10.1016/j.repc.2021.01.014" "estado" => "S300" "subdocumento" => "" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:1 [ "total" => 0 ] "idiomaDefecto" => "en" "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S0870255121004248?idApp=UINPBA00004E" ] ] "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S2174204921003664?idApp=UINPBA00004E" "url" => "/21742049/0000004000000012/v1_202112160943/S2174204921003664/v1_202112160943/en/main.assets" ] "en" => array:13 [ "idiomaDefecto" => true "cabecera" => "<span class="elsevierStyleTextfn">Editorial comment</span>" "titulo" => "Chronotropism during exercise. Methodological and conceptual inconsistencies" "tieneTextoCompleto" => true "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "955" "paginaFinal" => "956" ] ] "autores" => array:1 [ 0 => array:3 [ "autoresLista" => "Miguel Mendes" "autores" => array:1 [ 0 => array:3 [ "nombre" => "Miguel" "apellidos" => "Mendes" "email" => array:1 [ 0 => "miguel.mendes.md@gmail.com" ] ] ] "afiliaciones" => array:1 [ 0 => array:2 [ "entidad" => "Serviço de Cardiologia, CHLO, Hospital de Santa Cruz, Carnaxide, Portugal" "identificador" => "aff0005" ] ] ] ] "titulosAlternativos" => array:1 [ "pt" => array:1 [ "titulo" => "Cronotropismo no esforço. Inconsistências metodológicas e conceptuais" ] ] "textoCompleto" => "<span class="elsevierStyleSections"><p id="par0005" class="elsevierStylePara elsevierViewall">The authors of the article<a class="elsevierStyleCrossRef" href="#bib0005"><span class="elsevierStyleSup">1</span></a> to which this editorial refers assessed the effect of a cardiac rehabilitation program (CRP) on the chronotropic index (CIx) of patients after acute coronary syndrome (ACS), most of whom had been treated with several beta-blockers (BB) at different doses.</p><p id="par0010" class="elsevierStylePara elsevierViewall">The study of the chronotropic response to exercise is of the utmost importance because, although it is well established that the presence of chronotropic incompetence (CI) has a negative impact on patient progress, little is known about this undervalued topic, particularly because possible improvement is not acknowledged.</p><p id="par0015" class="elsevierStylePara elsevierViewall">The diagnosis of CI is complicated by the existence of several formulas for calculating the maximum predicted heart rate (MPHR), different criteria for defining HF, particularly in the context of BB.</p><p id="par0020" class="elsevierStylePara elsevierViewall">The authors retrospectively assessed a population of CRP participants, consisting of 543 consecutive patients after ACS, mostly male (14.9% female), asymptomatic (89% in New York Heart Association (NYHA) class I, who did not have significant impairment of left ventricular function (LVF). At admission and 12 months after ACS, about 86% and 87% of the cases were under BB, respectively.</p><p id="par0025" class="elsevierStylePara elsevierViewall">Chronotropism and functional capacity (FC) were studied using conventional exercise testing (ET) performed at three time points: before CRP, at the end of phase II, and 12 months after ACS. BB doses were converted into equivalents and the population was divided into three groups according to whether the dosage had been reduced, remained unchanged, or increased.</p><p id="par0030" class="elsevierStylePara elsevierViewall">Maximum predicted heart rate was calculated using the 220-age formula and Brawner's formula, and CI was diagnosed if the maximum heart rate (HRM) was less than 80% of the MPHR determined by the two formulas. Patients underwent eight to 24 sessions of aerobic and muscle strength training according to current international guidelines. After finishing the CRP there was an average reduction of 3 ppm at rest and an average increase of 5 ppm at peak exertion in the entire study population.</p><p id="par0035" class="elsevierStylePara elsevierViewall">Similarly, the CIx increased both when it was calculated using the 220-age formula or Brawner's formula. FC increased by about 2 METs after the program, and the gain was maintained 12 months after ACS, with a positive correlation between the increase in chronotopism and FC, which increased by about 0.37 estimated METs for each 1% of CIx calculated based on the 220-age formula, independent of age, gender, and BB dose.</p><p id="par0040" class="elsevierStylePara elsevierViewall">The authors correctly identify several limitations of their study. However, they did not consider the fact that CRP duration varied between eight and 24 sessions, which could have an impact on both FC and CI improvement, and that FC was assessed by conventional ET and not by cardiorespiratory ET, which would provide a more accurate measurement. It should be emphasized that cardiorespiratory ET, although recommended, is not considered mandatory in international recommendations in CRPs for patients with good LVF.</p><p id="par0045" class="elsevierStylePara elsevierViewall">They concluded that HF is improved by physical training in CRPs for patients after mildly symptomatic ACS, without compromised normal LVF, mostly on BB medication, regardless of the dose.</p><p id="par0050" class="elsevierStylePara elsevierViewall">The authors found that the classic (220-age) formula for calculating MPHR had a higher correlation with increasing FC relative to Brawner's formula.</p><p id="par0055" class="elsevierStylePara elsevierViewall">The calculation of CIx can be performed at submaximal<a class="elsevierStyleCrossRef" href="#bib0010"><span class="elsevierStyleSup">2</span></a> or maximal effort<a class="elsevierStyleCrossRefs" href="#bib0015"><span class="elsevierStyleSup">3,4</span></a> levels.</p><p id="par0060" class="elsevierStylePara elsevierViewall">Wilkoff<a class="elsevierStyleCrossRef" href="#bib0010"><span class="elsevierStyleSup">2</span></a> defined CIx as the quotient between the chronotropic reserve and the metabolic reserve at submaximal effort. CIx has the advantage of being adjusted to the age and FC of the individual and of being independent of the ergometer or protocol used. In normal adults, the percentage of chronotropic reserve is equal to the percentage of metabolic reserve. This concept means chronotropism can be assessed at any point in an ET using the formula: HR at staging is equal to (220-age HR at rest) multiplied by (METs at staging-1 dividing by METs reached at peak effort). The normal CIx is 1.0, accepting a range between 0.8 and 1.3. If it is ≤0.8 at a given point, CI is considered to exist.</p><p id="par0065" class="elsevierStylePara elsevierViewall">It can also be determined at maximal effort level, considering the value of MPHR based on age and one of several equations; calculating the respective percentage that was reached by the highest HR reached in ET interrupted by exhaustion. In this case, there are two difficulties: choosing the equation that best applies to the individual under study and ensuring that the degree of exhaustion has been reached.</p><p id="par0070" class="elsevierStylePara elsevierViewall">Regarding formulas, there is no consensus among experts and no univocal guidelines in international recommendations<a class="elsevierStyleCrossRefs" href="#bib0015"><span class="elsevierStyleSup">3,4</span></a>. Most exercise physiology laboratories continue to use the classical formula (HRM=220-age), although some studies have suggested that Brawner's formula (HRM=164-age × 0.7) would be the most appropriate for individuals with suspected or confirmed<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a> coronary heart disease, particularly for those who are undergoing BB therapy, and Tanaka's formula<a class="elsevierStyleCrossRef" href="#bib0030"><span class="elsevierStyleSup">6</span></a> (HRM=206-age × 0.88) for healthy individuals. Any of the proposed equations have an underlying standard deviation around 10-20 beats, which has led most centers to continue to use the equation HRM=220-age because it is easier to use, and they do not see significant usefulness in the alternatives.</p><p id="par0075" class="elsevierStylePara elsevierViewall">The second difficulty has to do with the certainty that the maximum HR has been reached. Usually this is performed subjectively when the patient or the ET performers consider that physical exhaustion has been reached. If we want to be rigorous, we have to perform a cardiorespiratory ET in which the intensity of effort that conditions the achievement of a respiratory quotient value greater than 1.10<a class="elsevierStyleCrossRef" href="#bib0020"><span class="elsevierStyleSup">4</span></a> must be reached. It is a gross error to consider reaching 85% of MPHR as a criterion to define a maximum effort test and decide upon its suspension.</p><p id="par0080" class="elsevierStylePara elsevierViewall">In fact, the best methodology for calculating CIx involves selecting a specific protocol to study chronotropism such as CAEP<a class="elsevierStyleCrossRef" href="#bib0035"><span class="elsevierStyleSup">7</span></a> and performing a cardiorespiratory exercise test in which a QR greater than 1.10 is achieved.</p><p id="par0085" class="elsevierStylePara elsevierViewall">After performing the ET, if we intend to assess CI by the HRM achieved, we need to choose one of its definitions. The definition of CI in medical literature is not agreed upon, and criteria for CI have been found based on percentages ranging from 70, 80 and 85% of MPHR, although most agree on the inability to reach 85% of MPH or 80% of chronotropic reserve (the difference between HR at rest and HR achieved during maximum effort) in individuals not on BB medication, and 62% of MPHR in patients on BB based on the formula HRM=220-age. Brawner's formula and others significantly underestimate the HRM, as can be seen in the work of Tiago Pimenta et al.</p><p id="par0090" class="elsevierStylePara elsevierViewall">The methodological difficulties and current inconsistencies in the definition of HF should encourage the conduct of prospective studies to establish an evaluation methodology and a more precise and clear definition, since the evaluation of chronotropism during exercise has already proven to have a high prognostic value for cardiovascular morbidity and mortality.</p><p id="par0095" class="elsevierStylePara elsevierViewall">In the context of cardiovascular disease, particularly in HF<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a>, both CIx and HR reduction in the first and third minutes of recovery, as well as HR variability are also predictors of poor prognosis, but are modifiable by aerobic exercise<a class="elsevierStyleCrossRef" href="#bib0045"><span class="elsevierStyleSup">9</span></a>. The study of HR variability during exertion requires the use of specific software not usually made available by exercise text equipment.</p><span id="sec0005" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0005">Conflicts of interest</span><p id="par0100" class="elsevierStylePara elsevierViewall">The authors have no conflicts of interest to declare.</p></span></span>" "textoCompletoSecciones" => array:1 [ "secciones" => array:2 [ 0 => array:2 [ "identificador" => "sec0005" "titulo" => "Conflicts of interest" ] 1 => array:1 [ "titulo" => "References" ] ] ] "pdfFichero" => "main.pdf" "tienePdf" => true "NotaPie" => array:1 [ 0 => array:2 [ "etiqueta" => "☆" "nota" => "<p class="elsevierStyleNotepara" id="npar0005">Please cite this article as: Mendes M. Cronotropismo no esforço. Inconsistências metodológicas e conceptuais. Rev Port Cardiol. 2021;40:955–956.</p>" ] ] "bibliografia" => array:2 [ "titulo" => "References" "seccion" => array:1 [ 0 => array:2 [ "identificador" => "bibs0005" "bibliografiaReferencia" => array:9 [ 0 => array:3 [ "identificador" => "bib0005" "etiqueta" => "1" "referencia" => array:1 [ 0 => array:2 [ "contribucion" => array:1 [ 0 => array:2 [ "titulo" => "Cardiac rehabilitation and improvement of chronotropic incompetence: is it the exercise or just the beta-blockers?" "autores" => array:1 [ 0 => array:2 [ "etal" => false "autores" => array:2 [ 0 => "J. Tiago Pimenta" 1 => "Afonso Rocha" ] ] ] ] ] "host" => array:1 [ 0 => array:1 [ "Revista" => array:3 [ "tituloSerie" => "Rev Port Cardiol." 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| Year/Month | Html | Total | |
|---|---|---|---|
| 2024 October | 335 | 52 | 387 |
| 2024 September | 444 | 58 | 502 |
| 2024 August | 517 | 96 | 613 |
| 2024 July | 486 | 57 | 543 |
| 2024 June | 343 | 55 | 398 |
| 2024 May | 302 | 67 | 369 |
| 2024 April | 305 | 58 | 363 |
| 2024 March | 305 | 34 | 339 |
| 2024 February | 258 | 48 | 306 |
| 2024 January | 360 | 63 | 423 |
| 2023 December | 207 | 54 | 261 |
| 2023 November | 323 | 92 | 415 |
| 2023 October | 281 | 51 | 332 |
| 2023 September | 139 | 42 | 181 |
| 2023 August | 176 | 36 | 212 |
| 2023 July | 137 | 29 | 166 |
| 2023 June | 145 | 17 | 162 |
| 2023 May | 139 | 48 | 187 |
| 2023 April | 120 | 40 | 160 |
| 2023 March | 141 | 43 | 184 |
| 2023 February | 114 | 27 | 141 |
| 2023 January | 107 | 48 | 155 |
| 2022 December | 105 | 54 | 159 |
| 2022 November | 89 | 47 | 136 |
| 2022 October | 135 | 43 | 178 |
| 2022 September | 99 | 65 | 164 |
| 2022 August | 140 | 52 | 192 |
| 2022 July | 186 | 74 | 260 |
| 2022 June | 187 | 52 | 239 |
| 2022 May | 116 | 43 | 159 |
| 2022 April | 116 | 77 | 193 |
| 2022 March | 122 | 60 | 182 |
| 2022 February | 80 | 55 | 135 |
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| 2021 December | 111 | 64 | 175 |
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